diff --git a/reactos/include/ndk/lpctypes.h b/reactos/include/ndk/lpctypes.h
index 444130ccc0a..44419618d5d 100644
--- a/reactos/include/ndk/lpctypes.h
+++ b/reactos/include/ndk/lpctypes.h
@@ -83,7 +83,11 @@ typedef enum _PORT_INFORMATION_CLASS
 //
 // Maximum message size that can be sent through an LPC Port without a section
 //
-#define PORT_MAXIMUM_MESSAGE_LENGTH     256
+#ifdef _WIN64
+#define PORT_MAXIMUM_MESSAGE_LENGTH 512
+#else
+#define PORT_MAXIMUM_MESSAGE_LENGTH 256
+#endif
 
 //
 // Portable LPC Types for 32/64-bit compatibility