diff --git a/Marlin/src/feature/bedlevel/ubl/ubl.h b/Marlin/src/feature/bedlevel/ubl/ubl.h
index 4e70c98c6f..f6e9ba0cd9 100644
--- a/Marlin/src/feature/bedlevel/ubl/ubl.h
+++ b/Marlin/src/feature/bedlevel/ubl/ubl.h
@@ -75,7 +75,7 @@ private:
   #endif
 
   static bool G29_parse_parameters() __O0;
-  static void shift_mesh_height();
+  static void shift_mesh_height(const float zoffs);
   static void probe_entire_mesh(const xy_pos_t &near, const bool do_ubl_mesh_map, const bool stow_probe, const bool do_furthest) __O0;
   static void tilt_mesh_based_on_probed_grid(const bool do_ubl_mesh_map);
   static bool smart_fill_one(const uint8_t x, const uint8_t y, const int8_t xdir, const int8_t ydir);
diff --git a/Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp b/Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp
index c4d5fbca6d..d97f1aa0af 100644
--- a/Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp
+++ b/Marlin/src/feature/bedlevel/ubl/ubl_G29.cpp
@@ -612,7 +612,7 @@ void unified_bed_leveling::G29() {
 
       case 5: adjust_mesh_to_mean(param.C_seen, param.C_constant); break;
 
-      case 6: shift_mesh_height(); break;
+      case 6: shift_mesh_height(param.C_constant); break;
     }
   }
 
@@ -752,10 +752,10 @@ void unified_bed_leveling::adjust_mesh_to_mean(const bool cflag, const float off
 /**
  * G29 P6 C<offset> : Shift Mesh Height by a uniform constant.
  */
-void unified_bed_leveling::shift_mesh_height() {
+void unified_bed_leveling::shift_mesh_height(const float zoffs) {
   GRID_LOOP(x, y)
     if (!isnan(z_values[x][y])) {
-      z_values[x][y] += param.C_constant;
+      z_values[x][y] += zoffs;
       TERN_(EXTENSIBLE_UI, ExtUI::onMeshUpdate(x, y, z_values[x][y]));
     }
 }