diff --git a/pkgs/development/interpreters/python/pypy/prebuilt.nix b/pkgs/development/interpreters/python/pypy/prebuilt.nix
index ef0350d93818..2737917c63b5 100644
--- a/pkgs/development/interpreters/python/pypy/prebuilt.nix
+++ b/pkgs/development/interpreters/python/pypy/prebuilt.nix
@@ -181,7 +181,7 @@ stdenv.mkDerivation {
     description = "Fast, compliant alternative implementation of the Python language (${pythonVersion})";
     mainProgram = "pypy";
     license = licenses.mit;
-    platforms = lib.mapAttrsToList (arch: _: arch) downloadUrls;
+    platforms = lib.attrNames downloadUrls;
   };
 
 }