diff --git a/pkgs/overlay.nix b/pkgs/overlay.nix
index a36961b..5977ab0 100644
--- a/pkgs/overlay.nix
+++ b/pkgs/overlay.nix
@@ -11,7 +11,7 @@ final: prev:
       paths = [ pmix.dev pmix.out ];
     };
   in prev.mpich.overrideAttrs (old: {
-    patches = [
+    patches = (old.patches or []) ++ [
       # See https://github.com/pmodels/mpich/issues/6946
       ./mpich-fix-hwtopo.patch
     ];