diff --git a/src/ytdl_sub/plugins/regex.py b/src/ytdl_sub/plugins/regex.py
index d8f65c8a..325649ea 100644
--- a/src/ytdl_sub/plugins/regex.py
+++ b/src/ytdl_sub/plugins/regex.py
@@ -231,7 +231,7 @@ class RegexOptions(OptionsDictValidator):
             return False
         for capture_group_default in regex_options.capture_group_defaults or []:
             parsed_default = parse(capture_group_default.format_string)
-            if parsed_default.variables.issubset(unresolved_variables):
+            if parsed_default.variables and parsed_default.variables.issubset(unresolved_variables):
                 return False
         return True
 
diff --git a/tests/e2e/plugins/test_regex.py b/tests/e2e/plugins/test_regex.py
index c0d824e5..58abb325 100644
--- a/tests/e2e/plugins/test_regex.py
+++ b/tests/e2e/plugins/test_regex.py
@@ -313,7 +313,8 @@ class TestRegex:
         with pytest.raises(
             ValidationException,
             match=re.escape(
-                "cannot use 'uid' as a capture group name because it is a defined variable"
+                "Cannot use the variable name uid because it exists as a built-in "
+                "ytdl-sub variable name."
             ),
         ):
             _ = Subscription.from_dict(
@@ -333,8 +334,8 @@ class TestRegex:
         with pytest.raises(
             ValidationException,
             match=re.escape(
-                "cannot use 'contains_regex_default' as a capture group name because it is a "
-                "defined variable"
+                "Override variable with name contains_regex_default cannot be used since it is "
+                "added by a plugin."
             ),
         ):
             _ = Subscription.from_dict(