1 files changed, 1 insertions, 1 deletions
diff --git a/lib/net/imap.rb b/lib/net/imap.rb
index 19e29c54f9..547e23e618 100644
--- a/lib/net/imap.rb
+++ b/lib/net/imap.rb
@@ -2748,7 +2748,7 @@ module Net
         token = match(T_ATOM)
         name = token.value.upcase
         case name
-        when /\A(?:ALERT|PARSE|READ-ONLY|READ-WRITE|TRYCREATE)\z/n
+        when /\A(?:ALERT|PARSE|READ-ONLY|READ-WRITE|TRYCREATE|NOMODSEQ)\z/n
           result = ResponseCode.new(name, nil)
         when /\A(?:PERMANENTFLAGS)\z/n
           match(T_SPACE)