3 files changed, 9 insertions, 6 deletions
diff --git a/scene/resources/surface_tool.cpp b/scene/resources/surface_tool.cpp
index 5ce3532d42..47933bd69a 100644
--- a/scene/resources/surface_tool.cpp
+++ b/scene/resources/surface_tool.cpp
@@ -299,6 +299,7 @@ void SurfaceTool::add_triangle_fan(const Vector<Vector3> &p_vertices, const Vect
 
 void SurfaceTool::add_index(int p_index) {
 	ERR_FAIL_COND(!begun);
+	ERR_FAIL_COND(p_index < 0);
 
 	format |= Mesh::ARRAY_FORMAT_INDEX;
 	index_array.push_back(p_index);
diff --git a/scene/resources/visual_shader.cpp b/scene/resources/visual_shader.cpp
index a296156bf5..d8e63e47be 100644
--- a/scene/resources/visual_shader.cpp
+++ b/scene/resources/visual_shader.cpp
@@ -1400,11 +1400,11 @@ bool VisualShader::has_func_name(RenderingServer::ShaderMode p_mode, const Strin
 }
 
 void VisualShader::_update_shader() const {
-	if (!dirty) {
+	if (!dirty.is_set()) {
 		return;
 	}
 
-	dirty = false;
+	dirty.clear();
 
 	StringBuilder global_code;
 	StringBuilder global_code_per_node;
@@ -1590,11 +1590,11 @@ void VisualShader::_update_shader() const {
 }
 
 void VisualShader::_queue_update() {
-	if (dirty) {
+	if (dirty.is_set()) {
 		return;
 	}
 
-	dirty = true;
+	dirty.set();
 	call_deferred("_update_shader");
 }
 
@@ -1614,7 +1614,7 @@ void VisualShader::_input_type_changed(Type p_type, int p_id) {
 }
 
 void VisualShader::rebuild() {
-	dirty = true;
+	dirty.set();
 	_update_shader();
 }
 
@@ -1668,6 +1668,7 @@ void VisualShader::_bind_methods() {
 }
 
 VisualShader::VisualShader() {
+	dirty.set();
 	for (int i = 0; i < TYPE_MAX; i++) {
 		Ref<VisualShaderNodeOutput> output;
 		output.instance();
diff --git a/scene/resources/visual_shader.h b/scene/resources/visual_shader.h
index f3f3caf15e..ef724c7650 100644
--- a/scene/resources/visual_shader.h
+++ b/scene/resources/visual_shader.h
@@ -32,6 +32,7 @@
 #define VISUAL_SHADER_H
 
 #include "core/string/string_builder.h"
+#include "core/templates/safe_refcount.h"
 #include "scene/gui/control.h"
 #include "scene/resources/shader.h"
 
@@ -99,7 +100,7 @@ private:
 
 	static RenderModeEnums render_mode_enums[];
 
-	volatile mutable bool dirty = true;
+	mutable SafeFlag dirty;
 	void _queue_update();
 
 	union ConnectionKey {