diff --git a/include/SDL_rwops.h b/include/SDL_rwops.h
index 61c30920e..acc499ffb 100644
--- a/include/SDL_rwops.h
+++ b/include/SDL_rwops.h
@@ -138,6 +138,7 @@ typedef struct SDL_RWops
         struct
         {
             void *data1;
+            int data2;
         } unknown;
     } hidden;