--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -15,6 +15,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
+#include <sys/resource.h>
 #include <asm/unistd.h>
 #include "init.h"
 #include "os.h"