diff --git a/prometheus_client/core.py b/prometheus_client/core.py
index f9334fa4..290749d6 100644
--- a/prometheus_client/core.py
+++ b/prometheus_client/core.py
@@ -875,7 +875,7 @@ def __exit__(self, typ, value, traceback):
 
     def __call__(self, f):
         def wrapped(func, *args, **kwargs):
-            with self:
+            with _HistogramTimer(self._histogram):
                 return func(*args, **kwargs)
         return decorate(f, wrapped)