diff --git a/utilities/ovs-dpctl-top.in b/utilities/ovs-dpctl-top.in
index 1708c2f37..f2d5bae6a 100755
--- a/utilities/ovs-dpctl-top.in
+++ b/utilities/ovs-dpctl-top.in
@@ -1007,7 +1007,7 @@ class FlowDB:
     def decay(self, decayTimeInSeconds):
         """ Decay content. """
         now = datetime.datetime.now()
-        for (key, value) in self._flows.items():
+        for (key, value) in list(self._flows.items()):
             (stats_dict, updateTime) = value
             delta = now - updateTime