diff --git a/builtin/blame.c b/builtin/blame.c
index 86100e9662..77707819af 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -1375,10 +1375,15 @@ static void get_ac_line(const char *inbuf, const char *what,
 	maillen = ident.mail_end - ident.mail_begin;
 	mailbuf = ident.mail_begin;
 
-	*time = strtoul(ident.date_begin, NULL, 10);
+	if (ident.date_begin && ident.date_end)
+		*time = strtoul(ident.date_begin, NULL, 10);
+	else
+		*time = 0;
 
-	len = ident.tz_end - ident.tz_begin;
-	strbuf_add(tz, ident.tz_begin, len);
+	if (ident.tz_begin && ident.tz_end)
+		strbuf_add(tz, ident.tz_begin, ident.tz_end - ident.tz_begin);
+	else
+		strbuf_addstr(tz, "(unknown)");
 
 	/*
 	 * Now, convert both name and e-mail using mailmap