diff --git a/lib/libc/minimal/include/fcntl.h b/lib/libc/minimal/include/fcntl.h
index caa79c91965..7737195b1c4 100644
--- a/lib/libc/minimal/include/fcntl.h
+++ b/lib/libc/minimal/include/fcntl.h
@@ -15,6 +15,6 @@
 #define F_GETFL 3
 #define F_SETFL 4
 
-int open(const char *name, int flags);
+int open(const char *name, int flags, ...);
 
 #endif /* ZEPHYR_LIB_LIBC_MINIMAL_INCLUDE_SYS_FCNTL_H_ */
diff --git a/lib/posix/fs.c b/lib/posix/fs.c
index 7cdbec4c992..d208d8b26a6 100644
--- a/lib/posix/fs.c
+++ b/lib/posix/fs.c
@@ -59,7 +59,7 @@ static inline void posix_fs_free_obj(struct posix_fs_desc *ptr)
  *
  * See IEEE 1003.1
  */
-int open(const char *name, int flags)
+int open(const char *name, int flags, ...)
 {
 	int rc, fd;
 	struct posix_fs_desc *ptr = NULL;