diff --git a/src/thread.h b/src/thread.h
--- a/src/thread.h
+++ b/src/thread.h
@@ -66,7 +66,7 @@ inline bool StartNewThread(std::thread *
 		return true;
 	} catch (const std::system_error& e) {
 		/* Something went wrong, the system we are running on might not support threads. */
-		DEBUG(misc, 1, "Can't create thread '%s': %s", name, e.what());
+		Debug(misc, 1, "Can't create thread '{}': {}", name, e.what());
 	}
 #endif