diff --git a/src/03_stacks_and_queues/queue_via_stacks.cpp b/src/03_stacks_and_queues/queue_via_stacks.cpp
index 8ebaa4d..59d17d9 100644
--- a/src/03_stacks_and_queues/queue_via_stacks.cpp
+++ b/src/03_stacks_and_queues/queue_via_stacks.cpp
@@ -1,6 +1,7 @@
 // Queue via Stacks: Implement a MyQueue class which implements a queue using
 // two stacks.
 
+#include <cstddef>
 #include <stack>
 
 // Solution