diff --git a/Marlin/src/gcode/parser.h b/Marlin/src/gcode/parser.h
index e14889d62f9..82843d62266 100644
--- a/Marlin/src/gcode/parser.h
+++ b/Marlin/src/gcode/parser.h
@@ -85,7 +85,7 @@ public:
   #endif
 
   #if ENABLED(DEBUG_GCODE_PARSER)
-    void debug();
+    static void debug();
   #endif
 
   // Reset is done before parsing
@@ -217,6 +217,9 @@ public:
 
   #if ENABLED(INCH_MODE_SUPPORT)
 
+    // Init linear units by constructor
+    GCodeParser() { set_input_linear_units(LINEARUNIT_MM); }
+
     inline static void set_input_linear_units(const LinearUnit units) {
       switch (units) {
         case LINEARUNIT_INCH: