diff --git a/sys/shell/shell_commands.c b/sys/shell/shell_commands.c
index 5223597d6c..932516a4b8 100644
--- a/sys/shell/shell_commands.c
+++ b/sys/shell/shell_commands.c
@@ -1,4 +1,5 @@
 #include <shell.h>
+#include <stdlib.h>
 
 const shell_command_t _shell_command_list[] = {
 #ifdef MODULE_PS