diff --git a/lib/irb/color.rb b/lib/irb/color.rb
index 0198838c6d..7a1d0c30ce 100644
--- a/lib/irb/color.rb
+++ b/lib/irb/color.rb
@@ -141,7 +141,7 @@ module IRB # :nodoc:
         seen[obj] = true
         block.call
       ensure
-        seen.delete(obj.object_id)
+        seen.delete(obj)
       end
 
       # Ripper::Lexer::Elem#state is supported on Ruby 2.5+