diff --git a/src/scriptapi.cpp b/src/scriptapi.cpp
index 8e4a43266..35e708a04 100644
--- a/src/scriptapi.cpp
+++ b/src/scriptapi.cpp
@@ -4415,8 +4415,8 @@ static int l_log(lua_State *L)
 	}
 	else
 	{
-		std::string levelname = lua_tostring(L, 1);
-		text = lua_tostring(L, 2);
+		std::string levelname = luaL_checkstring(L, 1);
+		text = luaL_checkstring(L, 2);
 		if(levelname == "error")
 			level = LMT_ERROR;
 		else if(levelname == "action")