Documentation/public-inbox-clone.pod | 12 ++++++++++++
 lib/PublicInbox/LeiMirror.pm         |  3 ++-

diff --git a/Documentation/public-inbox-clone.pod b/Documentation/public-inbox-clone.pod
index 1c31fbb3345000501ff2b814118d99e43e194f2e..cee9f76eec04cf39868a9d1a6719ed784ff5fc86 100644
--- a/Documentation/public-inbox-clone.pod
+++ b/Documentation/public-inbox-clone.pod
@@ -6,6 +6,8 @@ =head1 SYNOPSIS
 
 public-inbox-clone INBOX_URL [INBOX_DIR]
 
+public-inbox-clone ROOT_URL [DESTINATION]
+
 =head1 DESCRIPTION
 
 public-inbox-clone is a wrapper around C<git clone --mirror> for
@@ -81,6 +83,16 @@
 Force a remote public-inbox version (must be C<1> or C<2>).
 This is auto-detected by default, and this option exists mainly
 for testing.
+
+=item --objstore[=DIR]
+
+Enables space savings when the remote C<manifest.js.gz>
+includes C<forkgroup> entries as generated by grokmirror 2.x.
+
+If C<DIR> is not an absolute path, it is relative to the
+C<DESTINATION> directory.  If only C<--objstore> is specified
+without C<DIR>, then C<objstore> (C<$DESTINATION/objstore>)
+is the implied value of C<DIR>.
 
 =item -n
 
diff --git a/lib/PublicInbox/LeiMirror.pm b/lib/PublicInbox/LeiMirror.pm
index 6efe23fa9494c6a927ae4d5fe7edd9e61618bda2..2f96058a949c2d140ad1db595d047ede6aa5ec42 100644
--- a/lib/PublicInbox/LeiMirror.pm
+++ b/lib/PublicInbox/LeiMirror.pm
@@ -882,7 +882,8 @@ --inbox-config must be one of `always', `v2', `v1', or `never'
 
 		if (defined(my $os = $lei->{opt}->{objstore})) {
 			$os = 'objstore' if $os eq ''; # --objstore w/o args
-			$self->{-objstore} = "$self->{dst}/$os";
+			$os = "$self->{dst}/$os" if $os !~ m!\A/!;
+			$self->{-objstore} = $os;
 		}
 		local $LIVE;
 		my $iv = $lei->{opt}->{'inbox-version'} //