diff --git a/dom/xbl/nsBindingManager.cpp b/dom/xbl/nsBindingManager.cpp
index 9c41deb98e28..19f37d0dbb68 100644
--- a/dom/xbl/nsBindingManager.cpp
+++ b/dom/xbl/nsBindingManager.cpp
@@ -708,12 +708,12 @@ nsBindingManager::WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc,
   return NS_OK;
 }
 
-void
+bool
 nsBindingManager::EnumerateBoundContentBindings(
   const BoundContentBindingCallback& aCallback) const
 {
   if (!mBoundContentSet) {
-    return;
+    return true;
   }
 
   for (auto iter = mBoundContentSet->Iter(); !iter.Done(); iter.Next()) {
@@ -721,9 +721,13 @@ nsBindingManager::EnumerateBoundContentBindings(
     for (nsXBLBinding* binding = boundContent->GetXBLBinding();
          binding;
          binding = binding->GetBaseBinding()) {
-      aCallback(binding);
+      if (!aCallback(binding)) {
+        return false;
+      }
     }
   }
+
+  return true;
 }
 
 void
@@ -736,6 +740,7 @@ nsBindingManager::WalkAllRules(nsIStyleRuleProcessor::EnumFunc aFunc,
     if (ruleProcessor) {
       (*(aFunc))(ruleProcessor, aData);
     }
+    return true;
   });
 }
 
@@ -775,6 +780,7 @@ nsBindingManager::MediumFeaturesChanged(nsPresContext* aPresContext)
         rulesChanged = rulesChanged || thisChanged;
       }
     }
+    return true;
   });
 
   return rulesChanged;
@@ -794,6 +800,7 @@ nsBindingManager::UpdateBoundContentBindingsForServo(nsPresContext* aPresContext
     if (styleSet && styleSet->StyleSheetsHaveChanged()) {
       protoBinding->ComputeServoStyleSet(presContext);
     }
+    return true;
   });
 }
 
@@ -802,6 +809,7 @@ nsBindingManager::AppendAllSheets(nsTArray<StyleSheet*>& aArray)
 {
   EnumerateBoundContentBindings([&aArray](nsXBLBinding* aBinding) {
     aBinding->PrototypeBinding()->AppendStyleSheetsTo(aArray);
+    return true;
   });
 }
 
diff --git a/dom/xbl/nsBindingManager.h b/dom/xbl/nsBindingManager.h
index 0d381c9ac6d7..d86fea8c6f4a 100644
--- a/dom/xbl/nsBindingManager.h
+++ b/dom/xbl/nsBindingManager.h
@@ -196,9 +196,9 @@ protected:
   static void PostPAQEventCallback(nsITimer* aTimer, void* aClosure);
 
   // Enumerate each bound content's bindings (including its base bindings)
-  // in mBoundContentSet.
-  using BoundContentBindingCallback = std::function<void (nsXBLBinding*)>;
-  void EnumerateBoundContentBindings(
+  // in mBoundContentSet. Return false from the callback to stop enumeration.
+  using BoundContentBindingCallback = std::function<bool (nsXBLBinding*)>;
+  bool EnumerateBoundContentBindings(
     const BoundContentBindingCallback& aCallback) const;
 
 // MEMBER VARIABLES