diff --git a/include/xfs_inode.h b/include/xfs_inode.h
index ccf72d4a636a248303aa782896d6d7f661d12931..d7001937f9679e13492851d205c9e216e5cfa704 100644
--- a/include/xfs_inode.h
+++ b/include/xfs_inode.h
@@ -151,10 +151,13 @@ static inline bool xfs_inode_has_bigtime(struct xfs_inode *ip)
 	return ip->i_d.di_flags2 & XFS_DIFLAG2_BIGTIME;
 }
 
-typedef struct cred {
-	uid_t	cr_uid;
-	gid_t	cr_gid;
-} cred_t;
+/* Always set the child's GID to this value, even if the parent is setgid. */
+#define CRED_FORCE_GID	(1U << 0)
+struct cred {
+	uid_t		cr_uid;
+	gid_t		cr_gid;
+	unsigned int	cr_flags;
+};
 
 extern int	libxfs_inode_alloc (struct xfs_trans **, struct xfs_inode *,
 				mode_t, nlink_t, xfs_dev_t, struct cred *,
diff --git a/libxfs/util.c b/libxfs/util.c
index fd4906f8e98d72b7c1b276df3fe4c1ccfa277921..97413761e5f759067f755eeb32030238deb062be 100644
--- a/libxfs/util.c
+++ b/libxfs/util.c
@@ -301,7 +301,8 @@ libxfs_ialloc(
 	}
 
 	if (pip && (VFS_I(pip)->i_mode & S_ISGID)) {
-		ip->i_d.di_gid = pip->i_d.di_gid;
+		if (!(cr->cr_flags & CRED_FORCE_GID))
+			ip->i_d.di_gid = pip->i_d.di_gid;
 		if ((VFS_I(pip)->i_mode & S_ISGID) && (mode & S_IFMT) == S_IFDIR)
 			VFS_I(ip)->i_mode |= S_ISGID;
 	}
diff --git a/mkfs/proto.c b/mkfs/proto.c
index 3bba49171983a0bc3475152083c71f4331a6cdd8..b15f7652e56c5880d6ca0da9d1f7c735e835b600 100644
--- a/mkfs/proto.c
+++ b/mkfs/proto.c
@@ -360,7 +360,7 @@ parseproto(
 	xfs_trans_t	*tp;
 	int		val;
 	int		isroot = 0;
-	cred_t		creds;
+	struct cred_t	creds;
 	char		*value;
 	struct xfs_name	xname;
 
@@ -428,6 +428,7 @@ parseproto(
 	mode |= val;
 	creds.cr_uid = (int)getnum(getstr(pp), 0, 0, false);
 	creds.cr_gid = (int)getnum(getstr(pp), 0, 0, false);
+	creds.cr_flags = CRED_FORCE_GID;
 	xname.name = (unsigned char *)name;
 	xname.len = name ? strlen(name) : 0;
 	xname.type = 0;