diff --git a/lib/kiss/kiss_serial.rb b/lib/kiss/kiss_serial.rb
index 6eaeed6558c10554d0a0f68a114a4ecf563d41d0..476d07ebbe2fc0e26d2e41c15edce6c03380bf70 100644
--- a/lib/kiss/kiss_serial.rb
+++ b/lib/kiss/kiss_serial.rb
@@ -30,7 +30,9 @@ module Kiss
         protected
         def read_interface
             read_data = @serial.read(@read_bytes)
-            p read_data
+            if read_data != nil
+                p read_data
+            end
             if read_data
                 return read_data.chars.map { |c| c.ord }
             else