diff --git a/src/newgrf_config.cpp b/src/newgrf_config.cpp
--- a/src/newgrf_config.cpp
+++ b/src/newgrf_config.cpp
@@ -157,7 +157,7 @@ static void RemoveDuplicatesFromGRFConfi
 
 	for (prev = list, cur = list->next; cur != NULL; prev = cur, cur = cur->next) {
 		if (cur->grfid != list->grfid) continue;
-		assert(HASBIT(cur->flags, GCF_STATIC));
+
 		prev->next = cur->next;
 		ClearGRFConfig(&cur);
 		cur = prev; // Just go back one so it continues as normal later on