diff --git a/docs/skopeo-copy.1.md b/docs/skopeo-copy.1.md
index c3641884..fa698922 100644
--- a/docs/skopeo-copy.1.md
+++ b/docs/skopeo-copy.1.md
@@ -56,7 +56,7 @@ After copying the image, write the digest of the resulting image to the file.
 
 **--preserve-digests**
 
-Preserve the digests during copying. Fail if the digest cannot be preserved.
+Preserve the digests during copying. Fail if the digest cannot be preserved. Consider using `--all` at the same time.
 
 **--encrypt-layer** _ints_
 
diff --git a/docs/skopeo-sync.1.md b/docs/skopeo-sync.1.md
index 3e959414..abaa8cc3 100644
--- a/docs/skopeo-sync.1.md
+++ b/docs/skopeo-sync.1.md
@@ -66,7 +66,7 @@ Print usage statement.
 
 **--scoped** Prefix images with the source image path, so that multiple images with the same name can be stored at _destination_.
 
-**--preserve-digests** Preserve the digests during copying. Fail if the digest cannot be preserved.
+**--preserve-digests** Preserve the digests during copying. Fail if the digest cannot be preserved. Consider using `--all` at the same time.
 
 **--remove-signatures** Do not copy signatures, if any, from _source-image_. This is necessary when copying a signed image to a destination which does not support signatures.