diff --git a/fs_defs.h b/fs_defs.h
index 89de8b1..6db7fa4 100644
--- a/fs_defs.h
+++ b/fs_defs.h
@@ -52,6 +52,14 @@ typedef struct
     char        name[FS_MAX_ENTNAME_SIZE];
 } FSDirEntry;
 
+typedef void (*FSAsyncCallback)(void *pClient, void *pCmd, int result, void *context);
+typedef struct
+{
+    FSAsyncCallback userCallback;
+    void            *userContext;
+    void            *ioMsgQueue;
+} FSAsyncParams;
+
 
 #ifdef __cplusplus
 }