diff --git a/src/newgrf_railtype.cpp b/src/newgrf_railtype.cpp
--- a/src/newgrf_railtype.cpp
+++ b/src/newgrf_railtype.cpp
@@ -60,8 +60,8 @@
 
 /* virtual */ const SpriteGroup *RailTypeResolverObject::ResolveReal(const RealSpriteGroup *group) const
 {
-	if (group->num_loading > 0) return group->loading[0];
-	if (group->num_loaded  > 0) return group->loaded[0];
+	if (!group->loading.empty()) return group->loading[0];
+	if (!group->loaded.empty())  return group->loaded[0];
 	return nullptr;
 }