diff --git a/hashtable.c b/hashtable.c
index a4025be..244b453 100644
--- a/hashtable.c
+++ b/hashtable.c
@@ -106,9 +106,9 @@ bool hashtable_delete(hashtable* table, char* name) {
 		return false;
 }
 
-void hashtable_forall(hashtable* table, void (*callback)(char*, void*)) {
+void hashtable_forall(hashtable* table, void (*callback)(char*, void*, void*), void* userdata) {
 	size_t capacity = table->capacity;
 	hashtable_item* items = table->items;
 	for (size_t i = 0; i < capacity; i++)
-		callback(items[i].name, items[i].data);
+		callback(items[i].name, items[i].data, userdata);
 }
diff --git a/hashtable.h b/hashtable.h
index 967b735..b866665 100644
--- a/hashtable.h
+++ b/hashtable.h
@@ -33,4 +33,4 @@ void hashtable_set(hashtable* table, char* name, void* data);
 
 bool hashtable_delete(hashtable*, char*);
 
-void hashtable_forall(hashtable*, void (*)(char*, void*));
+void hashtable_forall(hashtable*, void (*)(char*, void*, void*), void*);