diff --git a/commit.go b/commit.go
index fc04e1e..3ccb5da 100644
--- a/commit.go
+++ b/commit.go
@@ -18,15 +18,19 @@ type Commit struct {
 	cast_ptr *C.git_commit
 }
 
-func (c Commit) Message() string {
-	return C.GoString(C.git_commit_message(c.cast_ptr))
+func (c *Commit) Message() string {
+	ret := C.GoString(C.git_commit_message(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) RawMessage() string {
-	return C.GoString(C.git_commit_message_raw(c.cast_ptr))
+func (c *Commit) RawMessage() string {
+	ret := C.GoString(C.git_commit_message_raw(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) ExtractSignature() (string, string, error) {
+func (c *Commit) ExtractSignature() (string, string, error) {
 
 	var c_signed C.git_buf
 	defer C.git_buf_free(&c_signed)
@@ -40,7 +44,7 @@ func (c Commit) ExtractSignature() (string, string, error) {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 	ret := C.git_commit_extract_signature(&c_signature, &c_signed, repo, oid.toC(), nil)
-
+	runtime.KeepAlive(oid)
 	if ret < 0 {
 		return "", "", MakeGitError(ret)
 	} else {
@@ -49,17 +53,20 @@ func (c Commit) ExtractSignature() (string, string, error) {
 
 }
 
-func (c Commit) Summary() string {
-	return C.GoString(C.git_commit_summary(c.cast_ptr))
+func (c *Commit) Summary() string {
+	ret := C.GoString(C.git_commit_summary(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) Tree() (*Tree, error) {
+func (c *Commit) Tree() (*Tree, error) {
 	var ptr *C.git_tree
 
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
 	err := C.git_commit_tree(&ptr, c.cast_ptr)
+	runtime.KeepAlive(c)
 	if err < 0 {
 		return nil, MakeGitError(err)
 	}
@@ -67,18 +74,24 @@ func (c Commit) Tree() (*Tree, error) {
 	return allocTree(ptr, c.repo), nil
 }
 
-func (c Commit) TreeId() *Oid {
-	return newOidFromC(C.git_commit_tree_id(c.cast_ptr))
+func (c *Commit) TreeId() *Oid {
+	ret := newOidFromC(C.git_commit_tree_id(c.cast_ptr))
+	runtime.KeepAlive(c)
+	return c
 }
 
-func (c Commit) Author() *Signature {
+func (c *Commit) Author() *Signature {
 	cast_ptr := C.git_commit_author(c.cast_ptr)
-	return newSignatureFromC(cast_ptr)
+	ret := newSignatureFromC(cast_ptr)
+	runtime.KeepAlive(c)
+	return ret
 }
 
-func (c Commit) Committer() *Signature {
+func (c *Commit) Committer() *Signature {
 	cast_ptr := C.git_commit_committer(c.cast_ptr)
-	return newSignatureFromC(cast_ptr)
+	ret := newSignatureFromC(cast_ptr)
+	runtime.KeepAlive(c)
+	return ret
 }
 
 func (c *Commit) Parent(n uint) *Commit {