diff --git a/LEGO1/mxdsaction.h b/LEGO1/mxdsaction.h
index 8cf20da0..a677741c 100644
--- a/LEGO1/mxdsaction.h
+++ b/LEGO1/mxdsaction.h
@@ -40,7 +40,7 @@ class MxDSAction : public MxDSObject
   virtual MxLong GetSomeTimingField(); // vtable+3c;
   virtual MxLong GetCurrentTime(); // vtable+40;
 
-  void ConcatData(MxU16 p_unkLength, void *p_unkData);
+  void AppendData(MxU16 p_unkLength, const char *p_unkData);
 
 private:
   MxU32 m_sizeOnDisk;