diff --git a/lib/kiss/kiss_serial.rb b/lib/kiss/kiss_serial.rb
index 6224cd9d3b6f09d19c0d513b9ff314a7974cd59b..051abd22843e745c0d1db308bf336dddf770f000 100644
--- a/lib/kiss/kiss_serial.rb
+++ b/lib/kiss/kiss_serial.rb
@@ -71,7 +71,7 @@ module Kiss
                 write_interface(MODE_END)
             end
 
-            if @serial == nil or @serial&.closed?
+            if @serial == nil or @serial.closed?
                 raise 'Attempting to close before the class has been started.'
             else
                 @serial.close