diff --git a/imapserver/search.go b/imapserver/search.go
index 46daa4e..c58aec9 100644
--- a/imapserver/search.go
+++ b/imapserver/search.go
@@ -128,6 +128,11 @@ func (c *conn) cmdxSearch(isUID bool, tag, cmd string, p *parser) {
 	})
 
 	if eargs == nil {
+		// In IMAP4rev1, an untagged SEARCH response is required. ../rfc/3501:2728
+		if len(uids) == 0 {
+			c.bwritelinef("* SEARCH")
+		}
+
 		// Old-style SEARCH response. We must spell out each number. So we may be splitting
 		// into multiple responses. ../rfc/9051:6809 ../rfc/3501:4833
 		for len(uids) > 0 {
diff --git a/imapserver/search_test.go b/imapserver/search_test.go
index 25b94b9..47128f0 100644
--- a/imapserver/search_test.go
+++ b/imapserver/search_test.go
@@ -36,10 +36,6 @@ this is html.
 func (tc *testconn) xsearch(nums ...uint32) {
 	tc.t.Helper()
 
-	if len(nums) == 0 {
-		tc.xnountagged()
-		return
-	}
 	tc.xuntagged(imapclient.UntaggedSearch(nums))
 }