diff --git a/irc/client_lookup_set.go b/irc/client_lookup_set.go
index 833e7876..2256c4f9 100644
--- a/irc/client_lookup_set.go
+++ b/irc/client_lookup_set.go
@@ -101,8 +101,10 @@ func (clients *ClientManager) SetNick(client *Client, session *Session, newNick
 	// on previous versions of Ergo:
 	if newNick != accountName {
 		// can't contain "disfavored" characters like <, or start with a $ because
-		// it collides with the massmessage mask syntax:
-		if strings.ContainsAny(newNick, disfavoredNameCharacters) || strings.HasPrefix(newNick, "$") {
+		// it collides with the massmessage mask syntax. '0' conflicts with the use of 0
+		// as a placeholder in WHOX (#1896):
+		if strings.ContainsAny(newNick, disfavoredNameCharacters) || strings.HasPrefix(newNick, "$") ||
+			newNick == "0" {
 			return "", errNicknameInvalid, false
 		}
 	}