diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index b1bb631be38d..f9f7f995e4ea 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -3855,9 +3855,13 @@ nsDocument::RemoveIDTargetObserver(nsIAtom* aID,
   if (!CheckGetElementByIdArg(aID))
     return;
 
-  nsIdentifierMapEntry *entry = GetElementByIdInternal(aID);
-  if (!entry)
+  nsIdentifierMapEntry *entry = mIdentifierMap.GetEntry(aID);
+  if (!entry) {
+    // We don't need to do the stuff that GetElementByIdInternal does;
+    // if there's no entry already in mIdentifierMap, then there's no
+    // callback to remove.
     return;
+  }
 
   entry->RemoveContentChangeCallback(aObserver, aData);
 }