diff --git a/nbresuse/api.py b/nbresuse/api.py
index b2d7f23..6ec3148 100644
--- a/nbresuse/api.py
+++ b/nbresuse/api.py
@@ -51,7 +51,7 @@ async def get(self):
             if config.cpu_limit != 0:
                 limits["cpu"] = {"cpu": config.cpu_limit}
                 if config.cpu_warning_threshold != 0:
-                    limits["cpu"]["warn"] = (config.cpu_limit - self.cpu_percent) < (
+                    limits["cpu"]["warn"] = (config.cpu_limit - cpu_percent) < (
                         config.cpu_limit * config.cpu_warning_threshold
                     )