diff --git a/gunicorn/arbiter.py b/gunicorn/arbiter.py
index dc89eb6e..1e7d829a 100644
--- a/gunicorn/arbiter.py
+++ b/gunicorn/arbiter.py
@@ -389,6 +389,8 @@ class Arbiter(object):
         """\
         Kill unused/idle workers
         """
+        if not self.timeout:
+            return
         for (pid, worker) in self.WORKERS.items():
             try:
                 if time.time() - worker.tmp.last_update() <= self.timeout: