diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index d7404c621ff7..b5afcfd0f861 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -191,6 +191,8 @@ int os_open_file(const char *file, struct openflags flags, int mode)
 		f |= O_TRUNC;
 	if (flags.e)
 		f |= O_EXCL;
+	if (flags.a)
+		f |= O_APPEND;
 
 	fd = open64(file, f, mode);
 	if (fd < 0)