diff --git a/Marlin/src/Marlin.cpp b/Marlin/src/Marlin.cpp
index 79d7ca0bde..b3da3af431 100644
--- a/Marlin/src/Marlin.cpp
+++ b/Marlin/src/Marlin.cpp
@@ -170,8 +170,8 @@ volatile bool wait_for_heatup = true;
 #endif
 
 // Inactivity shutdown
-static millis_t max_inactive_time = 0;
-static millis_t stepper_inactive_time = (DEFAULT_STEPPER_DEACTIVE_TIME) * 1000UL;
+millis_t max_inactive_time = 0,
+         stepper_inactive_time = (DEFAULT_STEPPER_DEACTIVE_TIME) * 1000UL;
 
 #if ENABLED(Z_DUAL_ENDSTOPS)
   float z_endstop_adj;
@@ -359,10 +359,6 @@ bool pin_is_protected(const int8_t pin) {
   return false;
 }
 
-#include "gcode/control/M18_M84.h"
-
-#include "gcode/control/M85.h"
-
 #include "gcode/config/M92.h"
 
 #if ENABLED(M100_FREE_MEMORY_WATCHER)
diff --git a/Marlin/src/Marlin.h b/Marlin/src/Marlin.h
index 26b90bfdd7..84bb67ba97 100644
--- a/Marlin/src/Marlin.h
+++ b/Marlin/src/Marlin.h
@@ -185,6 +185,9 @@ extern volatile bool wait_for_heatup;
   linear_fit* lsf_linear_fit(double x[], double y[], double z[], const int);
 #endif
 
+// Inactivity shutdown timer
+extern millis_t max_inactive_time, stepper_inactive_time;
+
 #if ENABLED(Z_DUAL_ENDSTOPS)
   extern float z_endstop_adj;
 #endif
diff --git a/Marlin/src/gcode/control/M18_M84.h b/Marlin/src/gcode/control/M18_M84.cpp
similarity index 88%
rename from Marlin/src/gcode/control/M18_M84.h
rename to Marlin/src/gcode/control/M18_M84.cpp
index 2a42f592d8..1fc3bb0b59 100644
--- a/Marlin/src/gcode/control/M18_M84.h
+++ b/Marlin/src/gcode/control/M18_M84.cpp
@@ -20,14 +20,19 @@
  *
  */
 
+#include "../gcode.h"
+#include "../../Marlin.h" // for stepper_inactive_time
+#include "../../module/stepper.h"
+
 #if ENABLED(AUTO_BED_LEVELING_UBL) && ENABLED(ULTRA_LCD)
-  extern bool defer_return_to_status;
+  #include "../../feature/bedlevel/bedlevel.h"
+  #include "../../lcd/ultralcd.h"
 #endif
 
 /**
  * M18, M84: Disable stepper motors
  */
-void gcode_M18_M84() {
+void GcodeSuite::M18_M84() {
   if (parser.seenval('S')) {
     stepper_inactive_time = parser.value_millis_from_seconds();
   }
diff --git a/Marlin/src/gcode/control/M85.h b/Marlin/src/gcode/control/M85.cpp
similarity index 91%
rename from Marlin/src/gcode/control/M85.h
rename to Marlin/src/gcode/control/M85.cpp
index 4570e66fed..2d8ab08b99 100644
--- a/Marlin/src/gcode/control/M85.h
+++ b/Marlin/src/gcode/control/M85.cpp
@@ -20,12 +20,14 @@
  *
  */
 
+#include "../gcode.h"
+#include "../../Marlin.h" // for max_inactive_time
+
 /**
  * M85: Set inactivity shutdown timer with parameter S<seconds>. To disable set zero (default)
  */
-void gcode_M85() {
+void GcodeSuite::M85() {
 
   if (parser.seen('S')) max_inactive_time = parser.value_millis_from_seconds();
 
 }
-
diff --git a/Marlin/src/gcode/gcode.cpp b/Marlin/src/gcode/gcode.cpp
index 84793f3919..30c39dfabf 100644
--- a/Marlin/src/gcode/gcode.cpp
+++ b/Marlin/src/gcode/gcode.cpp
@@ -116,8 +116,6 @@ void GcodeSuite::dwell(millis_t time) {
 //
 // Placeholders for non-migrated codes
 //
-extern void gcode_M18_M84();
-extern void gcode_M85();
 extern void gcode_M92();
 extern void gcode_M100();
 extern void gcode_M114();
@@ -497,12 +495,9 @@ void GcodeSuite::process_next_command() {
       case 83: M83(); break;      // M83: Set E axis relative mode
 
       case 18: // M18 => M84
-      case 84: // M84: Disable all steppers or set timeout
-        gcode_M18_M84();
-        break;
-      case 85: // M85: Set inactivity stepper shutdown timeout
-        gcode_M85();
-        break;
+      case 84: M18_M84(); break;  // M84: Disable all steppers or set timeout
+      case 85: M85(); break;      // M85: Set inactivity stepper shutdown timeout
+
       case 92: // M92: Set the steps-per-unit for one or more axes
         gcode_M92();
         break;
diff --git a/Marlin/src/lcd/ultralcd.h b/Marlin/src/lcd/ultralcd.h
index 1ceb972ee9..db17e6284f 100644
--- a/Marlin/src/lcd/ultralcd.h
+++ b/Marlin/src/lcd/ultralcd.h
@@ -80,6 +80,8 @@
 
   #if ENABLED(ULTIPANEL)
 
+    extern bool defer_return_to_status;
+
     // Function pointer to menu functions.
     typedef void (*screenFunc_t)();