diff --git a/colab/plugins/utils/signals.py b/colab/plugins/utils/signals.py
index 212ec9f..f698db7 100644
--- a/colab/plugins/utils/signals.py
+++ b/colab/plugins/utils/signals.py
@@ -2,7 +2,7 @@
 from abc import abstractmethod
 
 
-class AbstractSignal():
+class AbstractSignal(object)
 
     @abstractmethod
     def register_signal(self):
--
libgit2 0.21.2