diff --git a/include/villas/list.h b/include/villas/list.h
index ab79d6774..14de55a43 100644
--- a/include/villas/list.h
+++ b/include/villas/list.h
@@ -134,6 +134,9 @@ int list_set(struct list *l, int index, void *value);
  */
 ssize_t list_index(struct list *l, void *value);
 
+/** Extend the list to the given length by filling new slots with given value. */
+void list_extend(struct list *l, size_t len, void *val);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/list.c b/lib/list.c
index f8377c6e1..70f81a543 100644
--- a/lib/list.c
+++ b/lib/list.c
@@ -231,3 +231,9 @@ found:	pthread_mutex_unlock(&l->lock);
 
 	return f;
 }
+
+void list_extend(struct list *l, size_t len, void *val)
+{
+	while (list_length(l) < len)
+		list_push(l, val);
+}