diff --git a/include/proto/hlua_fcn.h b/include/proto/hlua_fcn.h
index 37d07ff..179d40c 100644
--- a/include/proto/hlua_fcn.h
+++ b/include/proto/hlua_fcn.h
@@ -1,6 +1,7 @@
 #ifndef _PROTO_HLUA_FCN_H
 #define _PROTO_HLUA_FCN_H
 
+void *hlua_checkudata(lua_State *L, int ud, int class_ref);
 int hlua_fcn_reg_core_fcn(lua_State *L);
 
 #endif /* _PROTO_HLUA_FCN_H */