diff --git a/include/proto/hlua_fcn.h b/include/proto/hlua_fcn.h
index e4ce5f0..291bd42 100644
--- a/include/proto/hlua_fcn.h
+++ b/include/proto/hlua_fcn.h
@@ -1,6 +1,8 @@
 #ifndef _PROTO_HLUA_FCN_H
 #define _PROTO_HLUA_FCN_H
 
+int hlua_checkboolean(lua_State *L, int index);
+
 void hlua_class_const_int(lua_State *L, const char *name, int value);
 void hlua_class_const_str(lua_State *L, const char *name, const char *value);
 void hlua_class_function(lua_State *L, const char *name, int (*function)(lua_State *L));