diff --git a/git-svn.perl b/git-svn.perl
index 00276c051b..58f5a7ac8f 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -500,6 +500,7 @@ sub do_git_init_db {
 		command_noisy('config', "$pfx.preserve-empty-dirs", 'true');
 		command_noisy('config', "$pfx.placeholder-filename", $$fname);
 	}
+	load_object_format();
 }
 
 sub init_subdir {
@@ -1977,9 +1978,15 @@ sub read_git_config {
 			}
 		}
 	}
+	load_object_format();
 	delete @$opts{@config_only} if @config_only;
 }
 
+sub load_object_format {
+	chomp(my $hash = `git config --get extensions.objectformat`);
+	$::oid_length = 64 if $hash eq 'sha256';
+}
+
 sub extract_metadata {
 	my $id = shift or return (undef, undef, undef);
 	my ($url, $rev, $uuid) = ($id =~ /^\s*git-svn-id:\s+(.*)\@(\d+)