diff --git a/x_robots_tag_middleware/middleware.py b/x_robots_tag_middleware/middleware.py
index 31c0bbc..5c796fe 100644
--- a/x_robots_tag_middleware/middleware.py
+++ b/x_robots_tag_middleware/middleware.py
@@ -18,6 +18,6 @@ def __call__(self, request):
 
         if settings.X_ROBOTS_TAG:
             response["X-Robots-Tag"] = ",".join(settings.X_ROBOTS_TAG)
-            logger.debug(f"x_robots_tag: {settings.X_ROBOTS_TAG}")
+            logger.debug("x_robots_tag: %s", settings.X_ROBOTS_TAG)
 
         return response