diff --git a/pkgs/development/python-modules/pytest/default.nix b/pkgs/development/python-modules/pytest/default.nix
index 93282218871..e0648285810 100644
--- a/pkgs/development/python-modules/pytest/default.nix
+++ b/pkgs/development/python-modules/pytest/default.nix
@@ -58,6 +58,12 @@ buildPythonPackage rec {
   checkPhase = ''
     runHook preCheck
     $out/bin/py.test -x testing/ -k "not test_collect_pyargs_with_testpaths" --ignore=testing/test_junitxml.py
+
+    # tests leave behind unreproducible pytest binaries in the output directory, remove:
+    find $out/lib -name "*-pytest-${version}.pyc" -delete
+    # specifically testing/test_assertion.py and testing/test_assertrewrite.py leave behind those:
+    find $out/lib -name "*opt-2.pyc" -delete
+
     runHook postCheck
   '';