diff --git a/tekuti/git.scm b/tekuti/git.scm
index 4bc7d60..3c9df31 100644
--- a/tekuti/git.scm
+++ b/tekuti/git.scm
@@ -167,7 +167,11 @@
                       "\n" 'suffix)))))
 
 (define (git-rev-parse rev)
-  (string-trim-both (git "rev-parse" rev)))
+  (or (false-if-exception
+       (let ((s (string-trim-both (call-with-input-file rev read-line))))
+         (and (= (string-length s) 40)
+              s)))
+      (git "rev-parse" rev)))
 
 (define (git-rev-list rev n)
   (let lp ((lines (string-split