diff --git a/__init__.py b/__init__.py
index f3276db..feeb761 100644
--- a/__init__.py
+++ b/__init__.py
@@ -155,7 +155,7 @@ def close_app(self, app: str) -> bool:
 
     def is_running(self, app: str) -> bool:
         """ check if a application is running"""
-        if self.match_window(app):
+        if self.wmctrl is not None and self.match_window(app):
             return True
         for p in self.match_process(app):
             return True