diff --git a/ext/standard/mail.c b/ext/standard/mail.c
index 8c68e3ba258..8fd0c09dde8 100644
--- a/ext/standard/mail.c
+++ b/ext/standard/mail.c
@@ -35,6 +35,7 @@
 #include "php_mail.h"
 #include "php_ini.h"
 #include "safe_mode.h"
+#include "exec.h"
 
 #if HAVE_SENDMAIL
 #ifdef PHP_WIN32