2 files changed, 39 insertions, 17 deletions

diff --git a/worktree_commit.go b/worktree_commit.go
index 7945af1..f62054b 100644
--- a/worktree_commit.go
+++ b/worktree_commit.go
@@ -45,29 +45,30 @@ func (w *Worktree) Commit(msg string, opts *CommitOptions) (plumbing.Hash, error
 		if err != nil {
 			return plumbing.ZeroHash, err
 		}
-
-		t, err := w.r.getTreeFromCommitHash(head.Hash())
+		headCommit, err := w.r.CommitObject(head.Hash())
 		if err != nil {
 			return plumbing.ZeroHash, err
 		}
 
-		treeHash = t.Hash
-		opts.Parents = []plumbing.Hash{head.Hash()}
-	} else {
-		idx, err := w.r.Storer.Index()
-		if err != nil {
-			return plumbing.ZeroHash, err
+		opts.Parents = nil
+		if len(headCommit.ParentHashes) != 0 {
+			opts.Parents = []plumbing.Hash{headCommit.ParentHashes[0]}
 		}
+	}
 
-		h := &buildTreeHelper{
-			fs: w.Filesystem,
-			s:  w.r.Storer,
-		}
+	idx, err := w.r.Storer.Index()
+	if err != nil {
+		return plumbing.ZeroHash, err
+	}
 
-		treeHash, err = h.BuildTree(idx, opts)
-		if err != nil {
-			return plumbing.ZeroHash, err
-		}
+	h := &buildTreeHelper{
+		fs: w.Filesystem,
+		s:  w.r.Storer,
+	}
+
+	treeHash, err = h.BuildTree(idx, opts)
+	if err != nil {
+		return plumbing.ZeroHash, err
 	}
 
 	commit, err := w.buildCommitObject(msg, opts, treeHash)
diff --git a/worktree_commit_test.go b/worktree_commit_test.go
index a3103b7..fee8b15 100644
--- a/worktree_commit_test.go
+++ b/worktree_commit_test.go
@@ -131,16 +131,37 @@ func (s *WorktreeSuite) TestCommitAmend(c *C) {
 	_, err = w.Commit("foo\n", &CommitOptions{Author: defaultSignature()})
 	c.Assert(err, IsNil)
 
+	util.WriteFile(fs, "bar", []byte("bar"), 0644)
+
+	_, err = w.Add("bar")
+	c.Assert(err, IsNil)
+
 	amendedHash, err := w.Commit("bar\n", &CommitOptions{Amend: true})
 	c.Assert(err, IsNil)
 
 	headRef, err := w.r.Head()
+	c.Assert(err, IsNil)
+
 	c.Assert(amendedHash, Equals, headRef.Hash())
+
 	commit, err := w.r.CommitObject(headRef.Hash())
 	c.Assert(err, IsNil)
 	c.Assert(commit.Message, Equals, "bar\n")
+	c.Assert(commit.NumParents(), Equals, 1)
+
+	stats, err := commit.Stats()
+	c.Assert(err, IsNil)
+	c.Assert(stats, HasLen, 2)
+	c.Assert(stats[0], Equals, object.FileStat{
+		Name:     "bar",
+		Addition: 1,
+	})
+	c.Assert(stats[1], Equals, object.FileStat{
+		Name:     "foo",
+		Addition: 1,
+	})
 
-	assertStorageStatus(c, s.Repository, 13, 11, 11, amendedHash)
+	assertStorageStatus(c, s.Repository, 14, 12, 11, amendedHash)
 }
 
 func (s *WorktreeSuite) TestAddAndCommitWithSkipStatus(c *C) {