diff --git a/test/test_protocol.py b/test/test_protocol.py
index f1afe10..14ca818 100644
--- a/test/test_protocol.py
+++ b/test/test_protocol.py
@@ -218,7 +218,7 @@ class Ei:
         while self.data:
             logger.debug("data pending dispatch: ", bytes=hexlify(self.data[:64]))
             header = MessageHeader.from_data(self.data)
-            logger.debug(f"dispatching message: ", header=header)
+            logger.debug("dispatching message: ", header=header)
             consumed = self.context.dispatch(self.data)
             if consumed == 0:
                 break