diff --git a/js/component/floor_plan_entity/point.js b/js/component/floor_plan_entity/point.js
index c1e71db..acab274 100644
--- a/js/component/floor_plan_entity/point.js
+++ b/js/component/floor_plan_entity/point.js
@@ -202,6 +202,12 @@ beestat.component.floor_plan_entity.point.prototype.after_mousedown_handler_ = f
 beestat.component.floor_plan_entity.point.prototype.after_mousemove_handler_ = function(e) {
   const snap_distance = 6;
 
+  // Debug/fix for #387
+  if (this.drag_start_entity_ === undefined) {
+    console.error('this.drag_start_entity_ is undefined (point)');
+    return;
+  }
+
   let desired_x = this.drag_start_entity_.x + (((e.clientX || e.touches[0].clientX) - this.drag_start_mouse_.x) * this.floor_plan_.get_scale());
   let desired_y = this.drag_start_entity_.y + (((e.clientY || e.touches[0].clientY) - this.drag_start_mouse_.y) * this.floor_plan_.get_scale());
 
diff --git a/js/component/floor_plan_entity/room.js b/js/component/floor_plan_entity/room.js
index dfb5e22..1c74fa0 100644
--- a/js/component/floor_plan_entity/room.js
+++ b/js/component/floor_plan_entity/room.js
@@ -462,6 +462,12 @@ beestat.component.floor_plan_entity.room.prototype.after_mousedown_handler_ = fu
 beestat.component.floor_plan_entity.room.prototype.after_mousemove_handler_ = function(e) {
   const self = this;
 
+  // Debug/fix for #387
+  if (this.drag_start_entity_ === undefined) {
+    console.error('this.drag_start_entity_ is undefined (room)');
+    return;
+  }
+
   let desired_x = this.drag_start_entity_.x + (((e.clientX || e.touches[0].clientX) - this.drag_start_mouse_.x) * this.floor_plan_.get_scale());
   let desired_y = this.drag_start_entity_.y + (((e.clientY || e.touches[0].clientY) - this.drag_start_mouse_.y) * this.floor_plan_.get_scale());
 
diff --git a/js/component/floor_plan_entity/wall.js b/js/component/floor_plan_entity/wall.js
index 2d3cec3..cdce5d1 100644
--- a/js/component/floor_plan_entity/wall.js
+++ b/js/component/floor_plan_entity/wall.js
@@ -358,6 +358,12 @@ beestat.component.floor_plan_entity.wall.prototype.set_xy = function(x, y, event
 beestat.component.floor_plan_entity.wall.prototype.after_mousemove_handler_ = function(e) {
   const snap_distance = 6;
 
+  // Debug/fix for #387
+  if (this.drag_start_entity_ === undefined) {
+    console.error('this.drag_start_entity_ is undefined (wall)');
+    return;
+  }
+
   if (this.is_vertical_() === true) {
     let desired_x = this.drag_start_entity_.x + (((e.clientX || e.touches[0].clientX) - this.drag_start_mouse_.x) * this.floor_plan_.get_scale());