diff --git a/osc_lib/cli/parseractions.py b/osc_lib/cli/parseractions.py
index 8125c18..0565372 100644
--- a/osc_lib/cli/parseractions.py
+++ b/osc_lib/cli/parseractions.py
@@ -35,7 +35,9 @@ class KeyValueAction(argparse.Action):
         if '=' in values:
             getattr(namespace, self.dest, {}).update([values.split('=', 1)])
         else:
-            getattr(namespace, self.dest, {}).pop(values, None)
+            msg = _("Expected 'key=value' type, "
+                    "but got: %s") % (str(values))
+            raise argparse.ArgumentTypeError(msg)
 
 
 class MultiKeyValueAction(argparse.Action):
diff --git a/osc_lib/tests/cli/test_parseractions.py b/osc_lib/tests/cli/test_parseractions.py
index 3225f93..beff04a 100644
--- a/osc_lib/tests/cli/test_parseractions.py
+++ b/osc_lib/tests/cli/test_parseractions.py
@@ -49,16 +49,13 @@ class TestKeyValueAction(utils.TestCase):
         self.assertDictEqual(expect, actual)
 
     def test_error_values(self):
-        results = self.parser.parse_args([
-            '--property', 'red',
-            '--property', 'green=100%',
-            '--property', 'blue',
-        ])
-
-        actual = getattr(results, 'property', {})
-        # There should be no red or blue
-        expect = {'green': '100%', 'format': '#rgb'}
-        self.assertDictEqual(expect, actual)
+        self.assertRaises(
+            argparse.ArgumentTypeError,
+            self.parser.parse_args,
+            [
+                '--property', 'red',
+            ]
+        )
 
 
 class TestMultiKeyValueAction(utils.TestCase):