diff --git a/config/sample-pwm-tool.cfg b/config/sample-pwm-tool.cfg
index 976f470b..4adcea6f 100644
--- a/config/sample-pwm-tool.cfg
+++ b/config/sample-pwm-tool.cfg
@@ -18,14 +18,14 @@ maximum_mcu_duration: 5
 # needs to be in default speed.
 
 [gcode_macro M3]
-default_parameter_S: 0
 gcode:
-    SET_PIN PIN=TOOL VALUE={S|float / 255}
+    {% set S = params.S|default(0.0)|float %}
+    SET_PIN PIN=TOOL VALUE={S / 255.0}
 
 [gcode_macro M4]
-default_parameter_S: 0
 gcode:
-    SET_PIN PIN=TOOL VALUE={S|float / 255}
+    {% set S = params.S|default(0.0)|float %}
+    SET_PIN PIN=TOOL VALUE={S / 255.0}
 
 [gcode_macro M5]
 gcode: