diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 26ecbd64c409..044836ad7392 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <stdlib.h>
+#include <string.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>