diff --git a/src/detect-lua-extensions.c b/src/detect-lua-extensions.c
index 9dd63f560c4e..367fb68d403c 100644
--- a/src/detect-lua-extensions.c
+++ b/src/detect-lua-extensions.c
@@ -298,7 +298,7 @@ static int LuaSetFlowvarByKey(lua_State *luastate)
     }
     keylen = lua_tonumber(luastate, 2);
     if (keylen < 0 || keylen > 0xff) {
-        LUA_ERROR("key len out of range: max 256");
+        LUA_ERROR("key len out of range: max 255");
     }
 
     if (!lua_isstring(luastate, 3)) {