diff --git a/src/process_wrap.cc b/src/process_wrap.cc
index 4a8628ef548..4b0f90a855b 100644
--- a/src/process_wrap.cc
+++ b/src/process_wrap.cc
@@ -2,6 +2,7 @@
 #include <handle_wrap.h>
 #include <pipe_wrap.h>
 #include <string.h>
+#include <stdlib.h>
 
 #define UNWRAP \
   assert(!args.Holder().IsEmpty()); \