diff --git a/nixos/modules/services/web-servers/h2o/default.nix b/nixos/modules/services/web-servers/h2o/default.nix
index 7e021281f91a..e359ea9671d8 100644
--- a/nixos/modules/services/web-servers/h2o/default.nix
+++ b/nixos/modules/services/web-servers/h2o/default.nix
@@ -5,11 +5,11 @@
   ...
 }:
 
-# TODO: ACME
 # TODO: Gems includes for Mruby
 # TODO: Recommended options
 let
   cfg = config.services.h2o;
+  inherit (config.security.acme) certs;
 
   inherit (lib)
     literalExpression
@@ -20,8 +20,62 @@ let
     types
     ;
 
+  mkCertOwnershipAssertion = import ../../../security/acme/mk-cert-ownership-assertion.nix lib;
+
   settingsFormat = pkgs.formats.yaml { };
 
+  getNames = name: vhostSettings: rec {
+    server = if vhostSettings.serverName != null then vhostSettings.serverName else name;
+    cert =
+      if lib.attrByPath [ "acme" "useHost" ] null vhostSettings == null then
+        server
+      else
+        vhostSettings.acme.useHost;
+  };
+
+  # Attrset with the virtual hosts relevant to ACME configuration
+  acmeEnabledHostsConfigs = lib.foldlAttrs (
+    acc: name: value:
+    if value.acme == null || (!value.acme.enable && value.acme.useHost == null) then
+      acc
+    else
+      let
+        names = getNames name value;
+        virtualHostConfig = value // {
+          serverName = names.server;
+          certName = names.cert;
+        };
+      in
+      acc ++ [ virtualHostConfig ]
+  ) [ ] cfg.hosts;
+
+  # Attrset with the ACME certificate names split by whether or not they depend
+  # on H2O serving challenges.
+  certNames =
+    let
+      partition =
+        acc: vhostSettings:
+        let
+          inherit (vhostSettings) certName;
+          isDependent = certs.${certName}.dnsProvider == null;
+        in
+        if isDependent && !(builtins.elem certName acc.dependent) then
+          acc // { dependent = acc.dependent ++ [ certName ]; }
+        else if !isDependent && !(builtins.elem certName acc.independent) then
+          acc // { independent = acc.independent ++ [ certName ]; }
+        else
+          acc;
+
+      certNames' = lib.lists.foldl partition {
+        dependent = [ ];
+        independent = [ ];
+      } acmeEnabledHostsConfigs;
+    in
+    certNames'
+    // {
+      all = certNames'.dependent ++ certNames'.independent;
+    };
+
   hostsConfig = lib.concatMapAttrs (
     name: value:
     let
@@ -29,56 +83,88 @@ let
         HTTP = lib.attrByPath [ "http" "port" ] cfg.defaultHTTPListenPort value;
         TLS = lib.attrByPath [ "tls" "port" ] cfg.defaultTLSListenPort value;
       };
-      serverName = if value.serverName != null then value.serverName else name;
-    in
-    # HTTP settings
-    lib.optionalAttrs (value.tls == null || value.tls.policy == "add") {
-      "${serverName}:${builtins.toString port.HTTP}" = value.settings // {
-        listen.port = port.HTTP;
-      };
-    }
-    # Redirect settings
-    // lib.optionalAttrs (value.tls != null && value.tls.policy == "force") {
-      "${serverName}:${builtins.toString port.HTTP}" = {
-        listen.port = port.HTTP;
-        paths."/" = {
-          redirect = {
-            status = value.tls.redirectCode;
-            url = "https://${serverName}:${builtins.toString port.TLS}";
-          };
-        };
-      };
-    }
-    # TLS settings
-    //
-      lib.optionalAttrs
-        (
-          value.tls != null
-          && builtins.elem value.tls.policy [
-            "add"
-            "only"
-            "force"
-          ]
-        )
+
+      names = getNames name value;
+
+      acmeSettings = lib.optionalAttrs (builtins.elem names.cert certNames.dependent) (
+        let
+          acmePort = 80;
+          acmeChallengePath = "/.well-known/acme-challenge";
+        in
         {
-          "${serverName}:${builtins.toString port.TLS}" = value.settings // {
-            listen =
-              let
-                identity = value.tls.identity;
-              in
-              {
-                port = port.TLS;
-                ssl = value.tls.extraSettings or { } // {
-                  inherit identity;
-                };
-              };
+          "${names.server}:${builtins.toString acmePort}" = {
+            listen.port = acmePort;
+            paths."${acmeChallengePath}/" = {
+              "file.dir" = value.acme.root + acmeChallengePath;
+            };
           };
         }
+      );
+
+      httpSettings =
+        lib.optionalAttrs (value.tls == null || value.tls.policy == "add") {
+          "${names.server}:${builtins.toString port.HTTP}" = value.settings // {
+            listen.port = port.HTTP;
+          };
+        }
+        // lib.optionalAttrs (value.tls != null && value.tls.policy == "force") {
+          "${names.server}:${builtins.toString port.HTTP}" = {
+            listen.port = port.HTTP;
+            paths."/" = {
+              redirect = {
+                status = value.tls.redirectCode;
+                url = "https://${names.server}:${builtins.toString port.TLS}";
+              };
+            };
+          };
+        };
+
+      tlsSettings =
+        lib.optionalAttrs
+          (
+            value.tls != null
+            && builtins.elem value.tls.policy [
+              "add"
+              "only"
+              "force"
+            ]
+          )
+          {
+            "${names.server}:${builtins.toString port.TLS}" = value.settings // {
+              listen =
+                let
+                  identity =
+                    value.tls.identity
+                    ++ lib.optional (builtins.elem names.cert certNames.all) {
+                      key-file = "${certs.${names.cert}.directory}/key.pem";
+                      certificate-file = "${certs.${names.cert}.directory}/fullchain.pem";
+                    };
+                in
+                {
+                  port = port.TLS;
+                  ssl = value.tls.extraSettings // {
+                    inherit identity;
+                  };
+                };
+            };
+          };
+    in
+    # With a high likelihood of HTTP & ACME challenges being on the same port,
+    # 80, do a recursive update to merge the 2 settings together
+    (lib.recursiveUpdate acmeSettings httpSettings) // tlsSettings
   ) cfg.hosts;
 
   h2oConfig = settingsFormat.generate "h2o.yaml" (
     lib.recursiveUpdate { hosts = hostsConfig; } cfg.settings
   );
+
+  # Executing H2O with our generated configuration; `mode` added as needed
+  h2oExe = ''${lib.getExe cfg.package} ${
+    lib.strings.escapeShellArgs [
+      "--conf"
+      "${h2oConfig}"
+    ]
+  }'';
 in
 {
   options = {
@@ -100,7 +186,7 @@ in
       package = lib.mkPackageOption pkgs "h2o" {
         example = ''
           pkgs.h2o.override {
-            withMruby = true;
+            withMruby = false;
           };
         '';
       };
@@ -123,21 +209,9 @@ in
         example = 8443;
       };
 
-      mode = mkOption {
-        type =
-          with types;
-          nullOr (enum [
-            "daemon"
-            "master"
-            "worker"
-            "test"
-          ]);
-        default = "master";
-        description = "Operating mode of H2O";
-      };
-
       settings = mkOption {
         type = settingsFormat.type;
+        default = { };
         description = "Configuration for H2O (see <https://h2o.examp1e.net/configure.html>)";
       };
 
@@ -189,6 +263,47 @@ in
   };
 
   config = mkIf cfg.enable {
+    assertions =
+      [
+        {
+          assertion =
+            !(builtins.hasAttr "hosts" h2oConfig)
+            || builtins.all (
+              host:
+              let
+                hasKeyPlusCert = attrs: (attrs.key-file or "") != "" && (attrs.certificate-file or "") != "";
+              in
+              # TLS not used
+              (lib.attrByPath [ "listen" "ssl" ] null host == null)
+              # TLS identity property
+              || (
+                builtins.hasAttr "identity" host
+                && builtins.length host.identity > 0
+                && builtins.all hasKeyPlusCert host.listen.ssl.identity
+              )
+              # TLS short-hand (was manually specified)
+              || (hasKeyPlusCert host.listen.ssl)
+            ) (lib.attrValues h2oConfig.hosts);
+          message = ''
+            TLS support will require at least one non-empty certificate & key
+            file. Use services.h2o.hosts.<name>.acme.enable,
+            services.h2o.hosts.<name>.acme.useHost,
+            services.h2o.hosts.<name>.tls.identity, or
+            services.h2o.hosts.<name>.tls.extraSettings.
+          '';
+        }
+      ]
+      ++ builtins.map (
+        name:
+        mkCertOwnershipAssertion {
+          cert = certs.${name};
+          groups = config.users.groups;
+          services = [
+            config.systemd.services.h2o
+          ] ++ lib.optional (certNames.all != [ ]) config.systemd.services.h2o-config-reload;
+        }
+      ) certNames.all;
+
     users = {
       users.${cfg.user} =
         {
@@ -201,14 +316,25 @@ in
     };
 
     systemd.services.h2o = {
-      description = "H2O web server service";
+      description = "H2O HTTP server";
       wantedBy = [ "multi-user.target" ];
-      after = [ "network.target" ];
+      wants = lib.concatLists (map (certName: [ "acme-finished-${certName}.target" ]) certNames.all);
+      # Since H2O will be hosting the challenges, H2O must be started
+      before = builtins.map (certName: "acme-${certName}.service") certNames.dependent;
+      after =
+        [ "network.target" ]
+        ++ builtins.map (certName: "acme-selfsigned-${certName}.service") certNames.all
+        ++ builtins.map (certName: "acme-${certName}.service") certNames.independent; # avoid loading self-signed key w/ real cert, or vice-versa
 
       serviceConfig = {
-        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
+        ExecStart = "${h2oExe} --mode 'master'";
+        ExecReload = [
+          "${h2oExe} --mode 'test'"
+          "${pkgs.coreutils}/bin/kill -HUP $MAINPID"
+        ];
         ExecStop = "${pkgs.coreutils}/bin/kill -s QUIT $MAINPID";
         User = cfg.user;
+        Group = cfg.group;
         Restart = "always";
         RestartSec = "10s";
         RuntimeDirectory = "h2o";
@@ -242,22 +368,66 @@ in
         CapabilitiesBoundingSet = [ "CAP_NET_BIND_SERVICE" ];
       };
 
-      script =
-        let
-          args =
-            [
-              "--conf"
-              "${h2oConfig}"
-            ]
-            ++ lib.optionals (cfg.mode != null) [
-              "--mode"
-              cfg.mode
-            ];
-        in
-        ''
-          ${lib.getExe cfg.package} ${lib.strings.escapeShellArgs args}
-        '';
+      preStart = "${h2oExe} --mode 'test'";
     };
-  };
 
+    # This service waits for all certificates to be available before reloading
+    # H2O configuration. `tlsTargets` are added to `wantedBy` + `before` which
+    # allows the `acme-finished-$cert.target` to signify the successful updating
+    # of certs end-to-end.
+    systemd.services.h2o-config-reload =
+      let
+        tlsTargets = map (certName: "acme-${certName}.target") certNames.all;
+        tlsServices = map (certName: "acme-${certName}.service") certNames.all;
+      in
+      mkIf (certNames.all != [ ]) {
+        wantedBy = tlsServices ++ [ "multi-user.target" ];
+        before = tlsTargets;
+        after = tlsServices;
+        unitConfig = {
+          ConditionPathExists = map (certName: "${certs.${certName}.directory}/fullchain.pem") certNames.all;
+          # Disable rate limiting for this since it may be triggered quickly
+          # a bunch of times if a lot of certificates are renewed in quick
+          # succession. The reload itself is cheap, so even doing a lot of them
+          # in a short burst is fine.
+          #
+          # FIXME: like Nginx’s FIXME, there’s probably a better way to do
+          # this.
+          StartLimitIntervalSec = 0;
+        };
+        serviceConfig = {
+          Type = "oneshot";
+          TimeoutSec = 60;
+          ExecCondition = "/run/current-system/systemd/bin/systemctl -q is-active h2o.service";
+          ExecStart = "/run/current-system/systemd/bin/systemctl reload h2o.service";
+        };
+      };
+
+    security.acme.certs =
+      let
+        mkCerts =
+          acc: vhostSettings:
+          if vhostSettings.acme.useHost == null then
+            let
+              hasRoot = vhostSettings.acme.root != null;
+            in
+            acc
+            // {
+              "${vhostSettings.serverName}" = {
+                group = mkDefault cfg.group;
+                # If `acme.root` is `null`, inherit `config.security.acme`.
+                # Since `config.security.acme.certs.<cert>.webroot`’s own
+                # default value should take precedence set priority higher than
+                # mkOptionDefault
+                webroot = lib.mkOverride (if hasRoot then 1000 else 2000) vhostSettings.acme.root;
+                # Also nudge dnsProvider to null in case it is inherited
+                dnsProvider = lib.mkOverride (if hasRoot then 1000 else 2000) null;
+                extraDomainNames = vhostSettings.serverAliases;
+              };
+            }
+          else
+            acc;
+      in
+      lib.lists.foldl mkCerts { } acmeEnabledHostsConfigs;
+  };
 }
diff --git a/nixos/modules/services/web-servers/h2o/vhost-options.nix b/nixos/modules/services/web-servers/h2o/vhost-options.nix
index 26abf8eb4f6a..f0ebf5a7b6d9 100644
--- a/nixos/modules/services/web-servers/h2o/vhost-options.nix
+++ b/nixos/modules/services/web-servers/h2o/vhost-options.nix
@@ -19,6 +19,18 @@ in
       example = "example.org";
     };
 
+    serverAliases = mkOption {
+      type = types.listOf types.nonEmptyStr;
+      default = [ ];
+      example = [
+        "www.example.org"
+        "example.org"
+      ];
+      description = ''
+        Additional names of virtual hosts served by this virtual host configuration.
+      '';
+    };
+
     http = mkOption {
       type = types.nullOr (
         types.submodule {
@@ -82,7 +94,7 @@ in
               '';
             };
             identity = mkOption {
-              type = types.nonEmptyListOf (
+              type = types.listOf (
                 types.submodule {
                   options = {
                     key-file = mkOption {
@@ -96,7 +108,7 @@ in
                   };
                 }
               );
-              default = null;
+              default = [ ];
               description = ''
                 Key / certificate pairs for the virtual host.
               '';
@@ -104,23 +116,21 @@ in
                 literalExpression
                   # nix
                   ''
-                    {
-                      indentities = [
-                        {
-                          key-file = "/path/to/rsa.key";
-                          certificate-file = "/path/to/rsa.crt";
-                        }
-                        {
-                          key-file = "/path/to/ecdsa.key";
-                          certificate-file = "/path/to/ecdsa.crt";
-                        }
-                      ];
-                    }
+                    [
+                      {
+                        key-file = "/path/to/rsa.key";
+                        certificate-file = "/path/to/rsa.crt";
+                      }
+                      {
+                        key-file = "/path/to/ecdsa.key";
+                        certificate-file = "/path/to/ecdsa.crt";
+                      }
+                    ]
                   '';
             };
             extraSettings = mkOption {
-              type = types.nullOr types.attrs;
-              default = null;
+              type = types.attrs;
+              default = { };
               description = ''
                 Additional TLS/SSL-related configuration options.
               '';
@@ -140,6 +150,49 @@ in
       description = "TLS options for virtual host";
     };
 
+    acme = mkOption {
+      type = types.nullOr (
+        types.addCheck (types.submodule {
+          options = {
+            enable = mkOption {
+              type = types.bool;
+              default = false;
+              description = ''
+                Whether to ask Let’s Encrypt to sign a certificate for this
+                virtual host. Alternatively, an existing host can be used thru
+                {option}`acme.useHost`.
+              '';
+            };
+            useHost = mkOption {
+              type = types.nullOr types.nonEmptyStr;
+              default = null;
+              description = ''
+                An existing Let’s Encrypt certificate to use for this virtual
+                host. This is useful if you have many subdomains and want to
+                avoid hitting the [rate
+                limit](https://letsencrypt.org/docs/rate-limits). Alternately,
+                you can generate a certificate through {option}`acme.enable`.
+                Note that this option neither creates any certificates nor does
+                it add subdomains to existing ones — you will need to create
+                them manually using [](#opt-security.acme.certs).
+              '';
+            };
+            root = mkOption {
+              type = types.nullOr types.path;
+              default = "/var/lib/acme/acme-challenge";
+              description = ''
+                Directory for the ACME challenge, which is **public**. Don’t put
+                certs or keys in here. Set to `null` to inherit from
+                config.security.acme.
+              '';
+            };
+          };
+        }) (a: (a.enable || a.useHost != null) && !(a.enable && a.useHost != null))
+      );
+      default = null;
+      description = "ACME options for virtual host.";
+    };
+
     settings = mkOption {
       type = types.attrs;
       description = ''
diff --git a/nixos/tests/step-ca.nix b/nixos/tests/step-ca.nix
index 4f2ff71c85e8..69b22bfd424a 100644
--- a/nixos/tests/step-ca.nix
+++ b/nixos/tests/step-ca.nix
@@ -1,4 +1,5 @@
-import ./make-test-python.nix ({ pkgs, ... }:
+import ./make-test-python.nix (
+  { pkgs, ... }:
   let
     test-certificates = pkgs.runCommandLocal "test-certificates" { } ''
       mkdir -p $out
@@ -10,83 +11,127 @@ import ./make-test-python.nix ({ pkgs, ... }:
   in
   {
     name = "step-ca";
-    nodes =
-      {
-        caserver =
-          { config, pkgs, ... }: {
-            environment.etc.password-file.source = "${test-certificates}/intermediate-password-file";
-            services.step-ca = {
-              enable = true;
-              address = "[::]";
-              port = 8443;
-              openFirewall = true;
-              intermediatePasswordFile = "/etc/${config.environment.etc.password-file.target}";
+    nodes = {
+      caserver =
+        { config, pkgs, ... }:
+        {
+          environment.etc.password-file.source = "${test-certificates}/intermediate-password-file";
+          services.step-ca = {
+            enable = true;
+            address = "[::]";
+            port = 8443;
+            openFirewall = true;
+            intermediatePasswordFile = "/etc/${config.environment.etc.password-file.target}";
+            settings = {
+              dnsNames = [ "caserver" ];
+              root = "${test-certificates}/root_ca.crt";
+              crt = "${test-certificates}/intermediate_ca.crt";
+              key = "${test-certificates}/intermediate_ca.key";
+              db = {
+                type = "badger";
+                dataSource = "/var/lib/step-ca/db";
+              };
+              authority = {
+                provisioners = [
+                  {
+                    type = "ACME";
+                    name = "acme";
+                  }
+                ];
+              };
+            };
+          };
+        };
+
+      caclient =
+        { config, pkgs, ... }:
+        {
+          security.acme.defaults.server = "https://caserver:8443/acme/acme/directory";
+          security.acme.defaults.email = "root@example.org";
+          security.acme.acceptTerms = true;
+
+          security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
+
+          networking.firewall.allowedTCPPorts = [
+            80
+            443
+          ];
+
+          services.nginx = {
+            enable = true;
+            virtualHosts = {
+              "caclient" = {
+                forceSSL = true;
+                enableACME = true;
+              };
+            };
+          };
+        };
+
+      caclientcaddy =
+        { config, pkgs, ... }:
+        {
+          security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
+
+          networking.firewall.allowedTCPPorts = [
+            80
+            443
+          ];
+
+          services.caddy = {
+            enable = true;
+            virtualHosts."caclientcaddy".extraConfig = ''
+              respond "Welcome to Caddy!"
+
+              tls caddy@example.org {
+                ca https://caserver:8443/acme/acme/directory
+              }
+            '';
+          };
+        };
+
+      caclienth2o =
+        { config, pkgs, ... }:
+        {
+          security.acme = {
+            acceptTerms = true;
+            defaults = {
+              server = "https://caserver:8443/acme/acme/directory";
+              email = "root@example.org";
+            };
+          };
+          security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
+
+          networking.firewall.allowedTCPPorts = [
+            80
+            443
+          ];
+
+          services.h2o = {
+            enable = true;
+            hosts."caclienth2o" = {
+              tls.policy = "force";
+              acme.enable = true;
               settings = {
-                dnsNames = [ "caserver" ];
-                root = "${test-certificates}/root_ca.crt";
-                crt = "${test-certificates}/intermediate_ca.crt";
-                key = "${test-certificates}/intermediate_ca.key";
-                db = {
-                  type = "badger";
-                  dataSource = "/var/lib/step-ca/db";
-                };
-                authority = {
-                  provisioners = [
-                    {
-                      type = "ACME";
-                      name = "acme";
-                    }
-                  ];
+                paths."/" = {
+                  "file.file" = "${pkgs.writeTextFile {
+                    name = "h2o_welcome.txt";
+                    text = "Welcome to H2O!";
+                  }}";
                 };
               };
             };
           };
+        };
 
-        caclient =
-          { config, pkgs, ... }: {
-            security.acme.defaults.server = "https://caserver:8443/acme/acme/directory";
-            security.acme.defaults.email = "root@example.org";
-            security.acme.acceptTerms = true;
-
-            security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
-
-            networking.firewall.allowedTCPPorts = [ 80 443 ];
-
-            services.nginx = {
-              enable = true;
-              virtualHosts = {
-                "caclient" = {
-                  forceSSL = true;
-                  enableACME = true;
-                };
-              };
-            };
-          };
-
-        caclientcaddy =
-          { config, pkgs, ... }: {
-            security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
-
-            networking.firewall.allowedTCPPorts = [ 80 443 ];
-
-            services.caddy = {
-              enable = true;
-              virtualHosts."caclientcaddy".extraConfig = ''
-                respond "Welcome to Caddy!"
-
-                tls caddy@example.org {
-                  ca https://caserver:8443/acme/acme/directory
-                }
-              '';
-            };
-          };
-
-        catester = { config, pkgs, ... }: {
+      catester =
+        { config, pkgs, ... }:
+        {
           security.pki.certificateFiles = [ "${test-certificates}/root_ca.crt" ];
         };
-      };
+    };
 
-    testScript =
+    testScript = # python
       ''
         catester.start()
         caserver.wait_for_unit("step-ca.service")
@@ -96,10 +141,13 @@ import ./make-test-python.nix ({ pkgs, ... }:
         catester.succeed("curl https://caclient/ | grep \"Welcome to nginx!\"")
 
         caclientcaddy.wait_for_unit("caddy.service")
-
-        # It's hard to know when caddy has finished the ACME
-        # dance with step-ca, so we keep trying to curl
-        # until succeess.
+        # It’s hard to know when Caddy has finished the ACME dance with
+        # step-ca, so we keep trying cURL until success.
         catester.wait_until_succeeds("curl https://caclientcaddy/ | grep \"Welcome to Caddy!\"")
+
+        caclienth2o.wait_for_unit("acme-finished-caclienth2o.target")
+        caclienth2o.wait_for_unit("h2o.service")
+        catester.succeed("curl https://caclienth2o/ | grep \"Welcome to H2O!\"")
       '';
-  })
+  }
+)
diff --git a/nixos/tests/web-servers/h2o/basic.nix b/nixos/tests/web-servers/h2o/basic.nix
index 673e082322bb..5432a3b04172 100644
--- a/nixos/tests/web-servers/h2o/basic.nix
+++ b/nixos/tests/web-servers/h2o/basic.nix
@@ -118,7 +118,6 @@ import ../../make-test-python.nix (
         assert "${sawatdi_chao_lok}" in http_hello_world_body
 
         tls_hello_world_head = server.succeed("curl -v --head --compressed --http2 --tlsv1.3 --fail-with-body 'https://${domain.TLS}:${builtins.toString port.TLS}/hello_world.rst'").lower()
-        print(tls_hello_world_head)
         assert "http/2 200" in tls_hello_world_head
         assert "server: h2o" in tls_hello_world_head
         assert "content-type: text/x-rst" in tls_hello_world_head
diff --git a/pkgs/by-name/h2/h2o/package.nix b/pkgs/by-name/h2/h2o/package.nix
index 66f1e5712bef..5afdcbeab9aa 100644
--- a/pkgs/by-name/h2/h2o/package.nix
+++ b/pkgs/by-name/h2/h2o/package.nix
@@ -16,6 +16,7 @@
   withMruby ? true,
   bison,
   ruby,
+  nixosTests,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -71,6 +72,10 @@ stdenv.mkDerivation (finalAttrs: {
     done
   '';
 
+  passthru = {
+    tests = { inherit (nixosTests) h2o; };
+  };
+
   meta = with lib; {
     description = "Optimized HTTP/1.x, HTTP/2, HTTP/3 server";
     homepage = "https://h2o.examp1e.net";