--- a/devtools/client/netmonitor/src/reducers/requests.js
+++ b/devtools/client/netmonitor/src/reducers/requests.js
@@ -233,16 +233,16 @@ function mapSet(map, key, value) {
   return newMap.set(key, value);
 }
 
 /**
  * Remove an item from existing map and return new map.
  */
 function mapDelete(map, key) {
   let newMap = mapNew(map);
-  newMap.requests.delete(key);
+  newMap.delete(key);
   return newMap;
 }
 
 module.exports = {
   Requests,
   requestsReducer,
 };