diff --git a/extensions/web/06_streams.js b/extensions/web/06_streams.js
index 79403442aa..48585e8be5 100644
--- a/extensions/web/06_streams.js
+++ b/extensions/web/06_streams.js
@@ -3018,9 +3018,8 @@
     if (byteSizeFunctionWeakMap.has(globalObject)) {
       return;
     }
-    byteSizeFunctionWeakMap.set(globalObject, function size(chunk) {
-      return chunk.byteLength;
-    });
+    const size = (chunk) => chunk.byteLength;
+    byteSizeFunctionWeakMap.set(globalObject, size);
   }
 
   class CountQueuingStrategy {
@@ -3071,9 +3070,8 @@
     if (countSizeFunctionWeakMap.has(globalObject)) {
       return;
     }
-    countSizeFunctionWeakMap.set(globalObject, function size() {
-      return 1;
-    });
+    const size = () => 1;
+    countSizeFunctionWeakMap.set(globalObject, size);
   }
 
   /** @template R */