diff --git a/Marlin/src/Marlin.cpp b/Marlin/src/Marlin.cpp
index ce77844daefa899ac285f57bbd94af9e59e82cbb..5259e3315054e650c0d10c611cfb6c912cebe10e 100644
--- a/Marlin/src/Marlin.cpp
+++ b/Marlin/src/Marlin.cpp
@@ -369,10 +369,6 @@ bool pin_is_protected(const int8_t pin) {
   return false;
 }
 
-#if ENABLED(TEMPERATURE_UNITS_SUPPORT)
-  #include "gcode/units/M149.h"
-#endif
-
 #if HAS_POWER_SWITCH
   #include "gcode/control/M80.h"
 #endif
diff --git a/Marlin/src/gcode/gcode.cpp b/Marlin/src/gcode/gcode.cpp
index 8622025007d21300d071ab44aabc26c87ee61a6f..9698998fab5fa877d824a6864afb609bb2998fe9 100644
--- a/Marlin/src/gcode/gcode.cpp
+++ b/Marlin/src/gcode/gcode.cpp
@@ -131,7 +131,6 @@ extern void gcode_M118();
 extern void gcode_M119();
 extern void gcode_M120();
 extern void gcode_M121();
-extern void gcode_M149();
 extern void gcode_M150();
 extern void gcode_M163();
 extern void gcode_M164();
@@ -547,9 +546,7 @@ void GcodeSuite::process_next_command() {
       #endif
 
       #if ENABLED(TEMPERATURE_UNITS_SUPPORT)
-        case 149: // M149: Set temperature units
-          gcode_M149();
-          break;
+        case 149: M149(); break;  // M149: Set temperature units
       #endif
 
       #if HAS_COLOR_LEDS
diff --git a/Marlin/src/gcode/units/M149.h b/Marlin/src/gcode/units/M149.cpp
similarity index 87%
rename from Marlin/src/gcode/units/M149.h
rename to Marlin/src/gcode/units/M149.cpp
index 7de58cb8e41a474f5558801e87225abc41db5086..307258816f258e42c0646ce4118ea4fd0150e71d 100644
--- a/Marlin/src/gcode/units/M149.h
+++ b/Marlin/src/gcode/units/M149.cpp
@@ -20,11 +20,19 @@
  *
  */
 
+#include "../../inc/MarlinConfig.h"
+
+#if ENABLED(TEMPERATURE_UNITS_SUPPORT)
+
+#include "../gcode.h"
+
 /**
  * M149: Set temperature units
  */
-void gcode_M149() {
+void GcodeSuite::M149() {
        if (parser.seenval('C')) parser.set_input_temp_units(TEMPUNIT_C);
   else if (parser.seenval('K')) parser.set_input_temp_units(TEMPUNIT_K);
   else if (parser.seenval('F')) parser.set_input_temp_units(TEMPUNIT_F);
 }
+
+#endif // TEMPERATURE_UNITS_SUPPORT