Index: lib/Brackup/Target/Filesystem.pm
===================================================================
--- lib/Brackup/Target/Filesystem.pm	(revision 163)
+++ lib/Brackup/Target/Filesystem.pm	(working copy)
@@ -37,15 +37,24 @@
 
 sub _diskpath {
     my ($self, $dig, $ext) = @_;
-    my @parts;
     my $fulldig = $dig;
     $dig =~ s/^\w+://; # remove the "hashtype:" from beginning
     $fulldig =~ s/:/./g if $self->{nocolons}; # Convert colons to dots if we've been asked to
-    while (length $dig && @parts < 4) {
-        $dig =~ s/^(.{1,4})//;
-        push @parts, $1;
+
+    # Old (1.05 and earlier) Brackup uses four four-character directories.
+    # We don't want to re-write chunks if they already exist in those paths.
+    my @four_parts;
+    my $four_part_dig = $dig;
+    while (length $four_part_dig && @four_parts < 4) {
+        $four_part_dig =~ s/^(.{1,4})//;
+        push @four_parts, $1;
     }
-    return $self->{path} . "/" . join("/", @parts) . "/$fulldig.$ext";
+    my $four_part_path = $self->{path} . "/" . join("/", @four_parts)
+                         . "/$fulldig.$ext";
+    return $four_part_path if stat $four_part_path;
+
+    my @two_parts = (substr($dig, 0, 2), substr($dig, 2, 2));
+    return $self->{path} . "/" . join("/", @two_parts) . "/$fulldig.$ext";
 }
 
 sub chunkpath {