diff --git a/builtin/am.c b/builtin/am.c
index 4f7f28a9dc..ffca4479d7 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -270,8 +270,11 @@ static int parse_key_value_squoted(char *buf, struct string_list *list)
 		struct string_list_item *item;
 		char *np;
 		char *cp = strchr(buf, '=');
-		if (!cp)
-			return -1;
+		if (!cp) {
+			np = strchrnul(buf, '\n');
+			return error(_("unable to parse '%.*s'"),
+				     (int) (np - buf), buf);
+		}
 		np = strchrnul(cp, '\n');
 		*cp++ = '\0';
 		item = string_list_append(list, buf);
@@ -280,7 +283,8 @@ static int parse_key_value_squoted(char *buf, struct string_list *list)
 		*np = '\0';
 		cp = sq_dequote(cp);
 		if (!cp)
-			return -1;
+			return error(_("unable to dequote value of '%s'"),
+				     item->string);
 		item->util = xstrdup(cp);
 	}
 	return 0;
@@ -308,6 +312,7 @@ static int read_author_script(struct am_state *state)
 	struct strbuf buf = STRBUF_INIT;
 	struct string_list kv = STRING_LIST_INIT_DUP;
 	int retval = -1; /* assume failure */
+	int i, name_i = -2, email_i = -2, date_i = -2, err = 0;
 	int fd;
 
 	assert(!state->author_name);
@@ -326,14 +331,38 @@ static int read_author_script(struct am_state *state)
 	if (parse_key_value_squoted(buf.buf, &kv))
 		goto finish;
 
-	if (kv.nr != 3 ||
-	    strcmp(kv.items[0].string, "GIT_AUTHOR_NAME") ||
-	    strcmp(kv.items[1].string, "GIT_AUTHOR_EMAIL") ||
-	    strcmp(kv.items[2].string, "GIT_AUTHOR_DATE"))
+	for (i = 0; i < kv.nr; i++) {
+		if (!strcmp(kv.items[i].string, "GIT_AUTHOR_NAME")) {
+			if (name_i != -2)
+				name_i = error(_("'GIT_AUTHOR_NAME' already given"));
+			else
+				name_i = i;
+		} else if (!strcmp(kv.items[i].string, "GIT_AUTHOR_EMAIL")) {
+			if (email_i != -2)
+				email_i = error(_("'GIT_AUTHOR_EMAIL' already given"));
+			else
+				email_i = i;
+		} else if (!strcmp(kv.items[i].string, "GIT_AUTHOR_DATE")) {
+			if (date_i != -2)
+				date_i = error(_("'GIT_AUTHOR_DATE' already given"));
+			else
+				date_i = i;
+		} else {
+			err = error(_("unknown variable '%s'"),
+				    kv.items[i].string);
+		}
+	}
+	if (name_i == -2)
+		error(_("missing 'GIT_AUTHOR_NAME'"));
+	if (email_i == -2)
+		error(_("missing 'GIT_AUTHOR_EMAIL'"));
+	if (date_i == -2)
+		error(_("missing 'GIT_AUTHOR_DATE'"));
+	if (date_i < 0 || email_i < 0 || date_i < 0 || err)
 		goto finish;
-	state->author_name = kv.items[0].util;
-	state->author_email = kv.items[1].util;
-	state->author_date = kv.items[2].util;
+	state->author_name = kv.items[name_i].util;
+	state->author_email = kv.items[email_i].util;
+	state->author_date = kv.items[date_i].util;
 	retval = 0;
 finish:
 	string_list_clear(&kv, !!retval);