diff --git a/src/cache.c3 b/src/cache.c3
index aeca415..62dbbf7 100644
--- a/src/cache.c3
+++ b/src/cache.c3
@@ -107,9 +107,9 @@ fn usz Cache.get_free_spot(&cache)
 	return 0;
 }
 
+<* @require g != null *>
 fn Value*? Cache.insert_at(&cache, Value* g, Key id, usz index)
 {
-	// TODO: verify index, g and id
 	Value* spot;
 
 	/* Set used and present */
@@ -124,12 +124,14 @@ fn Value*? Cache.insert_at(&cache, Value* g, Key id, usz index)
 }
 
 // Insert an element in the cache, returns the index
+<* @require g != null *>
 fn Value*? Cache.insert_new(&cache, Value* g, Key id)
 {
 	usz index = cache.get_free_spot();
 	return cache.insert_at(g, id, index);
 }
 
+<* @require g != null *>
 fn Value*? Cache.get_or_insert(&cache, Value* g, Key id, bool *is_new = null)
 {
 	Value*? c = cache.search(id);