diff --git a/builtin/am.c b/builtin/am.c
index e3dfd93c25..896cd0f827 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -98,6 +98,8 @@ struct am_state {
 	char *author_name;
 	char *author_email;
 	char *author_date;
+	char *committer_name;
+	char *committer_email;
 	char *msg;
 	size_t msg_len;
 
@@ -130,6 +132,8 @@ struct am_state {
  */
 static void am_state_init(struct am_state *state)
 {
+	const char *committer;
+	struct ident_split id;
 	int gpgsign;
 
 	memset(state, 0, sizeof(*state));
@@ -150,6 +154,14 @@ static void am_state_init(struct am_state *state)
 
 	if (!git_config_get_bool("commit.gpgsign", &gpgsign))
 		state->sign_commit = gpgsign ? "" : NULL;
+
+	committer = git_committer_info(IDENT_STRICT);
+	if (split_ident_line(&id, committer, strlen(committer)) < 0)
+		die(_("invalid committer: %s"), committer);
+	state->committer_name =
+		xmemdupz(id.name_begin, id.name_end - id.name_begin);
+	state->committer_email =
+		xmemdupz(id.mail_begin, id.mail_end - id.mail_end);
 }
 
 /**
@@ -161,6 +173,8 @@ static void am_state_release(struct am_state *state)
 	free(state->author_name);
 	free(state->author_email);
 	free(state->author_date);
+	free(state->committer_name);
+	free(state->committer_email);
 	free(state->msg);
 	argv_array_clear(&state->git_apply_opts);
 }
@@ -1556,7 +1570,7 @@ static void do_commit(const struct am_state *state)
 	struct object_id tree, parent, commit;
 	const struct object_id *old_oid;
 	struct commit_list *parents = NULL;
-	const char *reflog_msg, *author;
+	const char *reflog_msg, *author, *committer = NULL;
 	struct strbuf sb = STRBUF_INIT;
 
 	if (run_hook_le(NULL, "pre-applypatch", NULL))
@@ -1580,11 +1594,15 @@ static void do_commit(const struct am_state *state)
 			IDENT_STRICT);
 
 	if (state->committer_date_is_author_date)
-		setenv("GIT_COMMITTER_DATE",
-			state->ignore_date ? "" : state->author_date, 1);
+		committer = fmt_ident(state->committer_name,
+				      state->author_email, WANT_COMMITTER_IDENT,
+				      state->ignore_date ? NULL
+							 : state->author_date,
+				      IDENT_STRICT);
 
-	if (commit_tree(state->msg, state->msg_len, &tree, parents, &commit,
-			author, state->sign_commit))
+	if (commit_tree_extended(state->msg, state->msg_len, &tree, parents,
+				 &commit, author, committer, state->sign_commit,
+				 NULL))
 		die(_("failed to write commit object"));
 
 	reflog_msg = getenv("GIT_REFLOG_ACTION");
diff --git a/builtin/commit.c b/builtin/commit.c
index d3e7781e65..2785344fed 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1675,8 +1675,8 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	}
 
 	if (commit_tree_extended(sb.buf, sb.len, &active_cache_tree->oid,
-				 parents, &oid, author_ident.buf, sign_commit,
-				 extra)) {
+				 parents, &oid, author_ident.buf, NULL,
+				 sign_commit, extra)) {
 		rollback_index_files();
 		die(_("failed to write commit object"));
 	}
diff --git a/commit.c b/commit.c
index c7099daeac..fb63c22cc1 100644
--- a/commit.c
+++ b/commit.c
@@ -1324,8 +1324,8 @@ int commit_tree(const char *msg, size_t msg_len, const struct object_id *tree,
 	int result;
 
 	append_merge_tag_headers(parents, &tail);
-	result = commit_tree_extended(msg, msg_len, tree, parents, ret,
-				      author, sign_commit, extra);
+	result = commit_tree_extended(msg, msg_len, tree, parents, ret, author,
+				      NULL, sign_commit, extra);
 	free_commit_extra_headers(extra);
 	return result;
 }
@@ -1448,7 +1448,8 @@ N_("Warning: commit message did not conform to UTF-8.\n"
 int commit_tree_extended(const char *msg, size_t msg_len,
 			 const struct object_id *tree,
 			 struct commit_list *parents, struct object_id *ret,
-			 const char *author, const char *sign_commit,
+			 const char *author, const char *committer,
+			 const char *sign_commit,
 			 struct commit_extra_header *extra)
 {
 	int result;
@@ -1481,7 +1482,9 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 	if (!author)
 		author = git_author_info(IDENT_STRICT);
 	strbuf_addf(&buffer, "author %s\n", author);
-	strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
+	if (!committer)
+		committer = git_committer_info(IDENT_STRICT);
+	strbuf_addf(&buffer, "committer %s\n", committer);
 	if (!encoding_is_utf8)
 		strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);
 
diff --git a/commit.h b/commit.h
index 008a0fa4a0..8f4227ae5c 100644
--- a/commit.h
+++ b/commit.h
@@ -316,10 +316,9 @@ int commit_tree(const char *msg, size_t msg_len,
 
 int commit_tree_extended(const char *msg, size_t msg_len,
 			 const struct object_id *tree,
-			 struct commit_list *parents,
-			 struct object_id *ret, const char *author,
-			 const char *sign_commit,
-			 struct commit_extra_header *);
+			 struct commit_list *parents, struct object_id *ret,
+			 const char *author, const char *committer,
+			 const char *sign_commit, struct commit_extra_header *);
 
 struct commit_extra_header *read_commit_extra_headers(struct commit *, const char **);
 
diff --git a/ident.c b/ident.c
index e666ee4e59..7cbf223350 100644
--- a/ident.c
+++ b/ident.c
@@ -361,11 +361,15 @@ N_("\n"
 const char *fmt_ident(const char *name, const char *email,
 		      enum want_ident whose_ident, const char *date_str, int flag)
 {
-	static struct strbuf ident = STRBUF_INIT;
+	static int index;
+	static struct strbuf ident_pool[2] = { STRBUF_INIT, STRBUF_INIT };
 	int strict = (flag & IDENT_STRICT);
 	int want_date = !(flag & IDENT_NO_DATE);
 	int want_name = !(flag & IDENT_NO_NAME);
 
+	struct strbuf *ident = &ident_pool[index];
+	index = (index + 1) % ARRAY_SIZE(ident_pool);
+
 	if (!email) {
 		if (whose_ident == WANT_AUTHOR_IDENT && git_author_email.len)
 			email = git_author_email.buf;
@@ -421,25 +425,25 @@ const char *fmt_ident(const char *name, const char *email,
 			die(_("name consists only of disallowed characters: %s"), name);
 	}
 
-	strbuf_reset(&ident);
+	strbuf_reset(ident);
 	if (want_name) {
-		strbuf_addstr_without_crud(&ident, name);
-		strbuf_addstr(&ident, " <");
+		strbuf_addstr_without_crud(ident, name);
+		strbuf_addstr(ident, " <");
 	}
-	strbuf_addstr_without_crud(&ident, email);
+	strbuf_addstr_without_crud(ident, email);
 	if (want_name)
-			strbuf_addch(&ident, '>');
+		strbuf_addch(ident, '>');
 	if (want_date) {
-		strbuf_addch(&ident, ' ');
+		strbuf_addch(ident, ' ');
 		if (date_str && date_str[0]) {
-			if (parse_date(date_str, &ident) < 0)
+			if (parse_date(date_str, ident) < 0)
 				die(_("invalid date format: %s"), date_str);
 		}
 		else
-			strbuf_addstr(&ident, ident_default_date());
+			strbuf_addstr(ident, ident_default_date());
 	}
 
-	return ident.buf;
+	return ident->buf;
 }
 
 const char *fmt_name(enum want_ident whose_ident)
diff --git a/sequencer.c b/sequencer.c
index 6fd2674632..968a2d4ef3 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1408,8 +1408,8 @@ static int try_to_commit(struct repository *r,
 
 	reset_ident_date();
 
-	if (commit_tree_extended(msg->buf, msg->len, &tree, parents,
-				 oid, author, opts->gpg_sign, extra)) {
+	if (commit_tree_extended(msg->buf, msg->len, &tree, parents, oid,
+				 author, NULL, opts->gpg_sign, extra)) {
 		res = error(_("failed to write commit object"));
 		goto out;
 	}