diff --git a/geoip-block.py b/geoip-block.py
index 5cd45fa..86fee21 100644
--- a/geoip-block.py
+++ b/geoip-block.py
@@ -16,7 +16,7 @@ class Main():
 
     def run_sys_cmd(self, cmd):
         out, err = subprocess.Popen(cmd, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
-        if err.decode() is not '':
+        if err.decode() != '':
             raise SystemError(err.decode())
         return out.decode()