diff --git a/src/Classes/Project.gd b/src/Classes/Project.gd
index f6dd75a07..c3696ad95 100644
--- a/src/Classes/Project.gd
+++ b/src/Classes/Project.gd
@@ -204,6 +204,8 @@ func serialize() -> Dictionary:
 	for guide in guides:
 		if guide is SymmetryGuide:
 			continue
+		if !is_instance_valid(guide):
+			continue
 		var coords = guide.points[0].x
 		if guide.type == Guide.Types.HORIZONTAL:
 			coords = guide.points[0].y
diff --git a/src/UI/Rulers/Guide.gd b/src/UI/Rulers/Guide.gd
index e2f57d49d..1d0794a6b 100644
--- a/src/UI/Rulers/Guide.gd
+++ b/src/UI/Rulers/Guide.gd
@@ -63,10 +63,12 @@ func _draw() -> void:
 func outside_canvas() -> bool:
 	if type == Types.HORIZONTAL:
 		if points[0].y < 0 || points[0].y > project.size.y:
+			project.guides.erase(self)
 			queue_free()
 			return true
 	else:
 		if points[0].x < 0 || points[0].x > project.size.x:
+			project.guides.erase(self)
 			queue_free()
 			return true
 	return false