diff --git a/include/mntent.h b/include/mntent.h
index c0fed7fc..d03c414a 100644
--- a/include/mntent.h
+++ b/include/mntent.h
@@ -33,6 +33,7 @@ struct mntent
 FILE *setmntent(const char *, const char *);
 int endmntent(FILE *);
 struct mntent *getmntent(FILE *);
+struct mntent *getmntent_r(FILE *, struct mntent *, char *, int);
 int addmntent(FILE *, const struct mntent *);
 char *hasmntopt(const struct mntent *, const char *);