diff --git a/pkgs/development/python-modules/glean-parser/default.nix b/pkgs/development/python-modules/glean-parser/default.nix
index 704c556c0033..3cb8d83b7c8d 100644
--- a/pkgs/development/python-modules/glean-parser/default.nix
+++ b/pkgs/development/python-modules/glean-parser/default.nix
@@ -26,6 +26,12 @@ buildPythonPackage rec {
     hash = "sha256-PjOMNUnrz0kDfYEXv5Ni/9RIHn4Yylle6NJOK1Rb3SY=";
   };
 
+  postPatch = ''
+    substituteInPlace setup.py \
+      --replace "pytest-runner" "" \
+      --replace "MarkupSafe==2.0.1" "MarkupSafe"
+  '';
+
   nativeBuildInputs = [
     setuptools-scm
   ];
@@ -44,11 +50,6 @@ buildPythonPackage rec {
     pytestCheckHook
   ];
 
-  postPatch = ''
-    substituteInPlace setup.py \
-      --replace "pytest-runner" ""
-  '';
-
   disabledTests = [
     # https://bugzilla.mozilla.org/show_bug.cgi?id=1741668
     "test_validate_ping"