diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index f532d6d3bd28..79bc5f1338ed 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -126,7 +126,7 @@ static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
 		if (src_as->cell)
 			ctx->cell = afs_get_cell(src_as->cell);
 
-		if (size > PAGE_SIZE - 1)
+		if (size < 2 || size > PAGE_SIZE - 1)
 			return -EINVAL;
 
 		page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
@@ -140,7 +140,9 @@ static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
 		}
 
 		buf = kmap(page);
-		ret = vfs_parse_fs_string(fc, "source", buf, size);
+		ret = -EINVAL;
+		if (buf[size - 1] == '.')
+			ret = vfs_parse_fs_string(fc, "source", buf, size - 1);
 		kunmap(page);
 		put_page(page);
 		if (ret < 0)