diff --git a/pkgs/by-name/me/meson/package.nix b/pkgs/by-name/me/meson/package.nix
index 30727c12b71b..f0d0dd59e535 100644
--- a/pkgs/by-name/me/meson/package.nix
+++ b/pkgs/by-name/me/meson/package.nix
@@ -70,18 +70,22 @@ python3.pkgs.buildPythonApplication (finalAttrs: {
     ./007-freebsd-pkgconfig-path.patch
   ];
 
-  ${if python3.isPyPy then "postPatch" else null} = ''
-    substituteInPlace mesonbuild/modules/python.py \
-      --replace-fail "PythonExternalProgram('python3', mesonlib.python_command" \
-                      "PythonExternalProgram('${python3.meta.mainProgram}', mesonlib.python_command"
-    substituteInPlace mesonbuild/modules/python3.py \
-      --replace-fail "state.environment.lookup_binary_entry(mesonlib.MachineChoice.HOST, 'python3'" \
-                      "state.environment.lookup_binary_entry(mesonlib.MachineChoice.HOST, '${python3.meta.mainProgram}'"
-    substituteInPlace "test cases"/*/*/*.py "test cases"/*/*/*/*.py \
-      --replace-quiet '#!/usr/bin/env python3' '#!/usr/bin/env pypy3' \
-      --replace-quiet '#! /usr/bin/env python3' '#!/usr/bin/env pypy3'
-    chmod +x "test cases"/*/*/*.py "test cases"/*/*/*/*.py
-  '';
+  postPatch =
+    if python3.isPyPy then
+      ''
+        substituteInPlace mesonbuild/modules/python.py \
+          --replace-fail "PythonExternalProgram('python3', mesonlib.python_command" \
+                         "PythonExternalProgram('${python3.meta.mainProgram}', mesonlib.python_command"
+        substituteInPlace mesonbuild/modules/python3.py \
+          --replace-fail "state.environment.lookup_binary_entry(mesonlib.MachineChoice.HOST, 'python3'" \
+                         "state.environment.lookup_binary_entry(mesonlib.MachineChoice.HOST, '${python3.meta.mainProgram}'"
+        substituteInPlace "test cases"/*/*/*.py "test cases"/*/*/*/*.py \
+          --replace-quiet '#!/usr/bin/env python3' '#!/usr/bin/env pypy3' \
+          --replace-quiet '#! /usr/bin/env python3' '#!/usr/bin/env pypy3'
+        chmod +x "test cases"/*/*/*.py "test cases"/*/*/*/*.py
+      ''
+    else
+      null;
 
   build-system = [ python3.pkgs.setuptools ];