diff --git a/userprog/populate_stack.c b/userprog/populate_stack.c
index d353e7f38256316e85c5d7c154e46fe2dbe7cf06..2ac46526c03083a930291c596a521eb5ecc81dc4 100644
--- a/userprog/populate_stack.c
+++ b/userprog/populate_stack.c
@@ -5,6 +5,7 @@
  * Authored by Alex Stratford
  */
 
+#include <string.h>
 #include "threads/vaddr.h"
 #include "userprog/argument_parsing.h"