1 files changed, 1 insertions, 1 deletions

diff --git a/shared.c b/shared.c
index c7cd8a5..f20fb5c 100644
--- a/shared.c
+++ b/shared.c
@@ -339,40 +339,40 @@ int cgit_diff_files(const unsigned char *old_sha1,
         diff_params.flags = XDF_NEED_MINIMAL;
         emit_params.ctxlen = 3;
         emit_params.flags = XDL_EMIT_FUNCNAMES;
         emit_cb.outf = filediff_cb;
         emit_cb.priv = fn;
         xdl_diff(&file1, &file2, &diff_params, &emit_params, &emit_cb);
         return 0;
 }
 
 void cgit_diff_tree(const unsigned char *old_sha1,
                     const unsigned char *new_sha1,
                     filepair_fn fn)
 {
         struct diff_options opt;
         int ret;
 
         diff_setup(&opt);
         opt.output_format = DIFF_FORMAT_CALLBACK;
         opt.detect_rename = 1;
         opt.recursive = 1;
         opt.format_callback = cgit_diff_tree_cb;
         opt.format_callback_data = fn;
         diff_setup_done(&opt);
 
-        if (old_sha1)
+        if (old_sha1 && !is_null_sha1(old_sha1))
                 ret = diff_tree_sha1(old_sha1, new_sha1, "", &opt);
         else
                 ret = diff_root_tree_sha1(new_sha1, "", &opt);
         diffcore_std(&opt);
         diff_flush(&opt);
 }
 
 void cgit_diff_commit(struct commit *commit, filepair_fn fn)
 {
         unsigned char *old_sha1 = NULL;
 
         if (commit->parents)
                 old_sha1 = commit->parents->item->object.sha1;
         cgit_diff_tree(old_sha1, commit->object.sha1, fn);
 }