diff --git a/src/lua_script.c b/src/lua_script.c
index 506a888ea637c2f5cf489fb293183b320cc126d5..a7bd67456beeaeab371b588c1c3aab3e23a0b026 100644
--- a/src/lua_script.c
+++ b/src/lua_script.c
@@ -852,6 +852,7 @@ void LUA_InvalidateLevel(void)
 		LUA_InvalidateUserdata(&lines[i]);
 		LUA_InvalidateUserdata(&lines[i].tags);
 		LUA_InvalidateUserdata(&lines[i].args);
+		LUA_InvalidateUserdata(&lines[i].stringargs);
 		LUA_InvalidateUserdata(lines[i].sidenum);
 	}
 	for (i = 0; i < numsides; i++)
@@ -894,6 +895,7 @@ void LUA_InvalidateMapthings(void)
 		LUA_InvalidateUserdata(&mapthings[i]);
 		LUA_InvalidateUserdata(&mapthings[i].tags);
 		LUA_InvalidateUserdata(&mapthings[i].args);
+		LUA_InvalidateUserdata(&mapthings[i].stringargs);
 	}
 }