--- a/xpcom/glue/nsBaseHashtable.h
+++ b/xpcom/glue/nsBaseHashtable.h
@@ -111,32 +111,16 @@ public:
     if (!ent) {
       return UserDataType{};
     }
 
     return ent->mData;
   }
 
   /**
-   * Add key to the table if not already present, and return a reference to its
-   * value.  If key is not already in the table then the value is default
-   * constructed.
-   */
-  DataType& GetOrInsert(const KeyType& aKey)
-  {
-    EntryType* ent = this->GetEntry(aKey);
-    if (ent) {
-      return ent->mData;
-    }
-
-    ent = this->PutEntry(aKey);
-    return ent->mData;
-  }
-
-  /**
    * put a new value for the associated key
    * @param aKey the key to put
    * @param aData the new data
    * @return always true, unless memory allocation failed
    */
   void Put(KeyType aKey, const UserDataType& aData)
   {
     if (!Put(aKey, aData, mozilla::fallible)) {