diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index 5a1d1504d1..8e4853e9a2 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -7827,7 +7827,6 @@ inline void gcode_M115() {
     // CASE LIGHTS (M355)
     #if HAS_CASE_LIGHT
       SERIAL_PROTOCOLLNPGM("Cap:TOGGLE_LIGHTS:1");
-      bool USEABLE_HARDWARE_PWM(uint8_t pin);
       if (USEABLE_HARDWARE_PWM(CASE_LIGHT_PIN)) {
         SERIAL_PROTOCOLLNPGM("Cap:CASE_LIGHT_BRIGHTNESS:1");
       }