diff --git a/tests/test_duckargs.py b/tests/test_duckargs.py
index 5ea9033..0db3380 100644
--- a/tests/test_duckargs.py
+++ b/tests/test_duckargs.py
@@ -73,6 +73,14 @@ def test_env_all(self):
         os.environ["DUCKARGS_PRINT"] = "0"
         self._run_test("env_all")
 
+    def test_invalid_env_print(self):
+        os.environ["DUCKARGS_PRINT"] = "ksfensik"
+        self.assertRaises(RuntimeError, generate_python_code, ['duckargs', '-a'])
+
+    def test_invalid_env_comment(self):
+        os.environ["DUCKARGS_COMMENT"] = "ksfensik"
+        self.assertRaises(RuntimeError, generate_python_code, ['duckargs', '-a'])
+
     def test_duplicate_names(self):
         self.assertRaises(ValueError, generate_python_code, ['duckargs', '-a', '-a'])
         self.assertRaises(ValueError, generate_python_code, ['duckargs', '-a', '-b', '-a'])