diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
index 9a9705c9e3..b52a925dc6 100644
--- a/builtin/bisect--helper.c
+++ b/builtin/bisect--helper.c
@@ -85,6 +85,19 @@ static int one_of(const char *term, ...)
 	return res;
 }
 
+/*
+ * return code BISECT_INTERNAL_SUCCESS_MERGE_BASE
+ * and BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND are codes
+ * that indicate special success.
+ */
+
+static int is_bisect_success(enum bisect_error res)
+{
+	return !res ||
+		res == BISECT_INTERNAL_SUCCESS_1ST_BAD_FOUND ||
+		res == BISECT_INTERNAL_SUCCESS_MERGE_BASE;
+}
+
 static int write_in_file(const char *path, const char *mode, const char *format, va_list args)
 {
 	FILE *fp = NULL;
@@ -608,11 +621,12 @@ static enum bisect_error bisect_auto_next(struct bisect_terms *terms, const char
 	return bisect_next(terms, prefix);
 }
 
-static int bisect_start(struct bisect_terms *terms, int no_checkout,
+static enum bisect_error bisect_start(struct bisect_terms *terms, int no_checkout,
 			const char **argv, int argc)
 {
 	int i, has_double_dash = 0, must_write_terms = 0, bad_seen = 0;
-	int flags, pathspec_pos, res = 0;
+	int flags, pathspec_pos;
+	enum bisect_error res = BISECT_OK;
 	struct string_list revs = STRING_LIST_INIT_DUP;
 	struct string_list states = STRING_LIST_INIT_DUP;
 	struct strbuf start_head = STRBUF_INIT;
@@ -670,9 +684,12 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 			return error(_("unrecognized option: '%s'"), arg);
 		} else {
 			char *commit_id = xstrfmt("%s^{commit}", arg);
-			if (get_oid(commit_id, &oid) && has_double_dash)
-				die(_("'%s' does not appear to be a valid "
-				      "revision"), arg);
+			if (get_oid(commit_id, &oid) && has_double_dash) {
+				error(_("'%s' does not appear to be a valid "
+					"revision"), arg);
+				free(commit_id);
+				return BISECT_FAILED;
+			}
 
 			string_list_append(&revs, oid_to_hex(&oid));
 			free(commit_id);
@@ -750,14 +767,7 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 	 * Get rid of any old bisect state.
 	 */
 	if (bisect_clean_state())
-		return -1;
-
-	/*
-	 * In case of mistaken revs or checkout error, or signals received,
-	 * "bisect_auto_next" below may exit or misbehave.
-	 * We have to trap this to be able to clean up using
-	 * "bisect_clean_state".
-	 */
+		return BISECT_FAILED;
 
 	/*
 	 * Write new start state
@@ -771,7 +781,7 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 		}
 		if (update_ref(NULL, "BISECT_HEAD", &oid, NULL, 0,
 			       UPDATE_REFS_MSG_ON_ERR)) {
-			res = -1;
+			res = BISECT_FAILED;
 			goto finish;
 		}
 	}
@@ -783,25 +793,37 @@ static int bisect_start(struct bisect_terms *terms, int no_checkout,
 	for (i = 0; i < states.nr; i++)
 		if (bisect_write(states.items[i].string,
 				 revs.items[i].string, terms, 1)) {
-			res = -1;
+			res = BISECT_FAILED;
 			goto finish;
 		}
 
 	if (must_write_terms && write_terms(terms->term_bad,
 					    terms->term_good)) {
-		res = -1;
+		res = BISECT_FAILED;
 		goto finish;
 	}
 
 	res = bisect_append_log_quoted(argv);
 	if (res)
-		res = -1;
+		res = BISECT_FAILED;
 
 finish:
 	string_list_clear(&revs, 0);
 	string_list_clear(&states, 0);
 	strbuf_release(&start_head);
 	strbuf_release(&bisect_names);
+	if (res)
+		return res;
+
+	res = bisect_auto_next(terms, NULL);
+	/*
+	 * In case of mistaken revs or checkout error,
+	 * "bisect_auto_next" above may exit or misbehave.
+	 * We have to handle this to be able to clean up using
+	 * "bisect_clean_state".
+	 */
+	if (!is_bisect_success(res))
+		bisect_clean_state();
 	return res;
 }
 
diff --git a/git-bisect.sh b/git-bisect.sh
index 809be25424..cfb05c0511 100755
--- a/git-bisect.sh
+++ b/git-bisect.sh
@@ -49,27 +49,6 @@ bisect_head()
 	fi
 }
 
-bisect_start() {
-	git bisect--helper --bisect-start $@ || exit
-
-	#
-	# Change state.
-	# In case of mistaken revs or checkout error, or signals received,
-	# "bisect_auto_next" below may exit or misbehave.
-	# We have to trap this to be able to clean up using
-	# "bisect_clean_state".
-	#
-	trap 'git bisect--helper --bisect-clean-state' 0
-	trap 'exit 255' 1 2 3 15
-
-	#
-	# Check if we can proceed to the next bisect state.
-	#
-	git bisect--helper --bisect-auto-next || exit
-
-	trap '-' 0
-}
-
 bisect_skip() {
 	all=''
 	for arg in "$@"
@@ -163,8 +142,7 @@ bisect_replay () {
 		get_terms
 		case "$command" in
 		start)
-			cmd="bisect_start $rev $tail"
-			eval "$cmd" ;;
+			eval "git bisect--helper --bisect-start $rev $tail" ;;
 		"$TERM_GOOD"|"$TERM_BAD"|skip)
 			git bisect--helper --bisect-write "$command" "$rev" "$TERM_GOOD" "$TERM_BAD" || exit;;
 		terms)
@@ -264,7 +242,7 @@ case "$#" in
 	help)
 		git bisect -h ;;
 	start)
-		bisect_start "$@" ;;
+		git bisect--helper --bisect-start "$@" ;;
 	bad|good|new|old|"$TERM_BAD"|"$TERM_GOOD")
 		bisect_state "$cmd" "$@" ;;
 	skip)
