diff --git a/umu/umu_test.py b/umu/umu_test.py
index e08f6ce6a..66595897a 100644
--- a/umu/umu_test.py
+++ b/umu/umu_test.py
@@ -51,6 +51,7 @@ def setUp(self):
             "LD_PRELOAD": "",
             "WINEDLLPATH": "",
             "WINETRICKS_SUPER_QUIET": "",
+            "UMU_NO_RUNTIME": "",
         }
         self.user = getpwuid(os.getuid()).pw_name
         self.test_opts = "-foo -bar"