diff --git a/movement/shell.c b/movement/shell.c
index 8f146e5..6168f89 100644
--- a/movement/shell.c
+++ b/movement/shell.c
@@ -33,6 +33,7 @@
 
 #if __EMSCRIPTEN__
 #include <emscripten.h>
+#include <stdlib.h>
 #endif
 
 #include "watch.h"