diff --git a/lib/modules.nix b/lib/modules.nix
index 290b9ce0b698..ad71209a62a3 100644
--- a/lib/modules.nix
+++ b/lib/modules.nix
@@ -258,6 +258,7 @@ let
                     specialArgs
                     ;
                   _class = class;
+                  _prefix = prefix;
                 }
                 // specialArgs
               );
diff --git a/lib/tests/modules.sh b/lib/tests/modules.sh
index d0f25c283dcb..d7006d9c58fc 100755
--- a/lib/tests/modules.sh
+++ b/lib/tests/modules.sh
@@ -352,6 +352,9 @@ checkConfigOutput '^"submodule"$' options.submodule.type.description ./declare-s
 ## Paths should be allowed as values and work as expected
 checkConfigOutput '^true$' config.submodule.enable ./declare-submoduleWith-path.nix
 
+## _prefix module argument is available at import time and contains the prefix
+checkConfigOutput '^true$' config.foo.ok ./prefix-module-argument.nix
+
 ## deferredModule
 # default module is merged into nodes.foo
 checkConfigOutput '"beta"' config.nodes.foo.settingsDict.c ./deferred-module.nix
diff --git a/lib/tests/modules/prefix-module-argument.nix b/lib/tests/modules/prefix-module-argument.nix
new file mode 100644
index 000000000000..2cb854341a22
--- /dev/null
+++ b/lib/tests/modules/prefix-module-argument.nix
@@ -0,0 +1,17 @@
+{ lib, ... }:
+{
+  options.foo = lib.mkOption {
+    type = lib.types.submodule { };
+    default = { };
+  };
+
+  config = {
+    foo =
+      { _prefix, ... }:
+      assert _prefix == [ "foo" ];
+      {
+        options.ok = lib.mkOption { };
+        config.ok = true;
+      };
+  };
+}