diff --git a/pkgs/servers/mail/mailman/python.nix b/pkgs/servers/mail/mailman/python.nix
index 29d2f6c6d36a..933b8357a33d 100644
--- a/pkgs/servers/mail/mailman/python.nix
+++ b/pkgs/servers/mail/mailman/python.nix
@@ -28,6 +28,10 @@ python3.override {
           hash = "sha256-WF3FFrnrBCphnvCjnD19Vf6BvbTfCaUsnN3g0Hvxqn0=";
         };
       });
+
+      readme-renderer = super.readme-renderer.overridePythonAttrs (_: {
+        propagatedBuildInputs = [ self.cmarkgfm ];
+      });
     })
 
     overlay;