diff --git a/tests/runtests.py b/tests/runtests.py
index b21a3536ac..a111ef1436 100755
--- a/tests/runtests.py
+++ b/tests/runtests.py
@@ -148,5 +148,7 @@ if __name__ == "__main__":
     options, args = parser.parse_args()
     if options.settings:
         os.environ['DJANGO_SETTINGS_MODULE'] = options.settings
-
+    elif "DJANGO_SETTINGS_MODULE" not in os.environ:
+        parser.error("DJANGO_SETTINGS_MODULE is not set in the environment. "
+                      "Set it or use --settings.")
     django_tests(int(options.verbosity), args)