diff --git a/pkgs/by-name/_9/_9pfs/package.nix b/pkgs/by-name/_9/_9pfs/package.nix
index d57ea3abcb37..54d50ee3cf44 100644
--- a/pkgs/by-name/_9/_9pfs/package.nix
+++ b/pkgs/by-name/_9/_9pfs/package.nix
@@ -19,7 +19,7 @@ stdenv.mkDerivation (finalAttrs: {
   };
 
   postPatch = ''
-    substituteInPlace Makefile --replace "pkg-config" "$PKG_CONFIG"
+    substituteInPlace Makefile --replace-fail "pkg-config" "$PKG_CONFIG"
   '';
 
   makeFlags = [