diff --git a/include/spdlog/details/thread_pool-inl.h b/include/spdlog/details/thread_pool-inl.h
index 43220f43..2789abfa 100644
--- a/include/spdlog/details/thread_pool-inl.h
+++ b/include/spdlog/details/thread_pool-inl.h
@@ -113,7 +113,7 @@ bool SPDLOG_INLINE thread_pool::process_next_msg_()
     }
 
     default: {
-        assert(false && "Unexpected async_msg_type");
+        assert(false);
     }
     }