diff --git a/lisp/info-xref.el b/lisp/info-xref.el
index 7887909037b..95e9a1e55f7 100644
--- a/lisp/info-xref.el
+++ b/lisp/info-xref.el
@@ -79,9 +79,11 @@ info-xref-subfile-p
 which exists, then consider FILENAME a subfile.  This is an
 imperfect test, probably ought to open up the purported top file
 and see what subfiles it says."
-  (and (string-match "\\`\\(\\([^-]*-\\)*[^-]*\\)-[0-9]+\\(.*\\)\\'" filename)
-       (file-exists-p (concat (match-string 1 filename)
-                              (match-string 3 filename)))))
+  (let ((nondir (file-name-nondirectory filename)))
+    (and (string-match "\\`\\(\\([^-]*-\\)*[^-]*\\)-[0-9]+\\(.*\\)\\'" nondir)
+         (file-exists-p (concat (file-name-directory filename)
+                                (match-string 1 nondir)
+                                (match-string 3 nondir))))))

 (defmacro info-xref-with-file (filename &rest body)
   ;; checkdoc-params: (filename body)