diff --git a/nixos/modules/services/web-apps/immich.nix b/nixos/modules/services/web-apps/immich.nix
index 28e89709afde..86b29e657cd6 100644
--- a/nixos/modules/services/web-apps/immich.nix
+++ b/nixos/modules/services/web-apps/immich.nix
@@ -231,6 +231,11 @@ in
         assertion = !isPostgresUnixSocket -> cfg.secretsFile != null;
         message = "A secrets file containing at least the database password must be provided when unix sockets are not used.";
       }
+      {
+        # When removing this assertion, please adjust the nixosTests accordingly.
+        assertion = cfg.database.enable -> lib.versionOlder config.services.postgresql.package.version "17";
+        message = "Immich doesn't support PostgreSQL 17+, yet.";
+      }
     ];
 
     services.postgresql = mkIf cfg.database.enable {
diff --git a/nixos/tests/web-apps/immich-public-proxy.nix b/nixos/tests/web-apps/immich-public-proxy.nix
index f711e56abb48..1516156223ce 100644
--- a/nixos/tests/web-apps/immich-public-proxy.nix
+++ b/nixos/tests/web-apps/immich-public-proxy.nix
@@ -30,6 +30,9 @@
         port = 8002;
         settings.ipp.responseHeaders."X-NixOS" = "Rules";
       };
+
+      # TODO: Remove when PostgreSQL 17 is supported.
+      services.postgresql.package = pkgs.postgresql_16;
     };
 
   testScript = ''
diff --git a/nixos/tests/web-apps/immich.nix b/nixos/tests/web-apps/immich.nix
index 550a1630bda8..d716e50b8906 100644
--- a/nixos/tests/web-apps/immich.nix
+++ b/nixos/tests/web-apps/immich.nix
@@ -18,6 +18,9 @@
         enable = true;
         environment.IMMICH_LOG_LEVEL = "verbose";
       };
+
+      # TODO: Remove when PostgreSQL 17 is supported.
+      services.postgresql.package = pkgs.postgresql_16;
     };
 
   testScript = ''