diff --git a/quiz/src/assertions.cpp b/quiz/src/assertions.cpp
index 6f7e227f7..5e9b19b29 100644
--- a/quiz/src/assertions.cpp
+++ b/quiz/src/assertions.cpp
@@ -1,4 +1,5 @@
 #include <ion.h>
+#include <stdlib.h>
 #include <quiz.h>
 
 void quiz_assert(bool condition) {