diff --git a/klippy/klippy.py b/klippy/klippy.py
index e2c580bc..327af461 100644
--- a/klippy/klippy.py
+++ b/klippy/klippy.py
@@ -84,7 +84,7 @@ class Printer:
             and self.start_args.get('debuginput') is not None):
             self.request_exit('error_exit')
     def add_object(self, name, obj):
-        if obj in self.objects:
+        if name in self.objects:
             raise self.config_error(
                 "Printer object '%s' already created" % (name,))
         self.objects[name] = obj