diff --git a/include/rapidjson/document.h b/include/rapidjson/document.h
index 1cdc29c..41f92e8 100644
--- a/include/rapidjson/document.h
+++ b/include/rapidjson/document.h
@@ -75,7 +75,7 @@ class GenericDocument;
     User can define this to use CrtAllocator or MemoryPoolAllocator.
 */
 #ifndef RAPIDJSON_DEFAULT_ALLOCATOR
-#define RAPIDJSON_DEFAULT_ALLOCATOR MemoryPoolAllocator<CrtAllocator>
+#define RAPIDJSON_DEFAULT_ALLOCATOR ::RAPIDJSON_NAMESPACE::MemoryPoolAllocator<::RAPIDJSON_NAMESPACE::CrtAllocator>
 #endif
 
 /*! \def RAPIDJSON_DEFAULT_STACK_ALLOCATOR