diff --git a/tests/IronPython.Tests/Cases/IronPythonCasesManifest.ini b/tests/IronPython.Tests/Cases/IronPythonCasesManifest.ini
index 57e527834..4715f7714 100644
--- a/tests/IronPython.Tests/Cases/IronPythonCasesManifest.ini
+++ b/tests/IronPython.Tests/Cases/IronPythonCasesManifest.ini
@@ -191,7 +191,6 @@ NotParallelSafe=true # Uses a temporary module with a fixed name
 RetryCount=2
 
 [IronPython.modules.misc.test_zlib]
-NotParallelSafe=true # test_data.gz
 
 [IronPython.modules.system_related.test_nt]
 RunCondition=NOT $(IS_POSIX)