diff --git a/editor/plugins/material_editor_plugin.cpp b/editor/plugins/material_editor_plugin.cpp
index 27a16fd3dd9..f282d391ff5 100644
--- a/editor/plugins/material_editor_plugin.cpp
+++ b/editor/plugins/material_editor_plugin.cpp
@@ -429,7 +429,7 @@ bool SpatialMaterialConversionPlugin::handles(const Ref<Resource> &p_resource) c
 	Ref<SpatialMaterial> mat = p_resource;
 	return mat.is_valid();
 }
-Ref<Resource> SpatialMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) {
+Ref<Resource> SpatialMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) const {
 
 	Ref<SpatialMaterial> mat = p_resource;
 	ERR_FAIL_COND_V(!mat.is_valid(), Ref<Resource>());
@@ -475,7 +475,7 @@ bool ParticlesMaterialConversionPlugin::handles(const Ref<Resource> &p_resource)
 	Ref<ParticlesMaterial> mat = p_resource;
 	return mat.is_valid();
 }
-Ref<Resource> ParticlesMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) {
+Ref<Resource> ParticlesMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) const {
 
 	Ref<ParticlesMaterial> mat = p_resource;
 	ERR_FAIL_COND_V(!mat.is_valid(), Ref<Resource>());
@@ -513,7 +513,7 @@ bool CanvasItemMaterialConversionPlugin::handles(const Ref<Resource> &p_resource
 	Ref<CanvasItemMaterial> mat = p_resource;
 	return mat.is_valid();
 }
-Ref<Resource> CanvasItemMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) {
+Ref<Resource> CanvasItemMaterialConversionPlugin::convert(const Ref<Resource> &p_resource) const {
 
 	Ref<CanvasItemMaterial> mat = p_resource;
 	ERR_FAIL_COND_V(!mat.is_valid(), Ref<Resource>());
diff --git a/editor/plugins/material_editor_plugin.h b/editor/plugins/material_editor_plugin.h
index 80a5c535b8c..31a927d83f9 100644
--- a/editor/plugins/material_editor_plugin.h
+++ b/editor/plugins/material_editor_plugin.h
@@ -109,7 +109,7 @@ class SpatialMaterialConversionPlugin : public EditorResourceConversionPlugin {
 public:
 	virtual String converts_to() const;
 	virtual bool handles(const Ref<Resource> &p_resource) const;
-	virtual Ref<Resource> convert(const Ref<Resource> &p_resource);
+	virtual Ref<Resource> convert(const Ref<Resource> &p_resource) const;
 };
 
 class ParticlesMaterialConversionPlugin : public EditorResourceConversionPlugin {
@@ -117,7 +117,7 @@ class ParticlesMaterialConversionPlugin : public EditorResourceConversionPlugin
 public:
 	virtual String converts_to() const;
 	virtual bool handles(const Ref<Resource> &p_resource) const;
-	virtual Ref<Resource> convert(const Ref<Resource> &p_resource);
+	virtual Ref<Resource> convert(const Ref<Resource> &p_resource) const;
 };
 
 class CanvasItemMaterialConversionPlugin : public EditorResourceConversionPlugin {
@@ -125,7 +125,7 @@ class CanvasItemMaterialConversionPlugin : public EditorResourceConversionPlugin
 public:
 	virtual String converts_to() const;
 	virtual bool handles(const Ref<Resource> &p_resource) const;
-	virtual Ref<Resource> convert(const Ref<Resource> &p_resource);
+	virtual Ref<Resource> convert(const Ref<Resource> &p_resource) const;
 };
 
 #endif // MATERIAL_EDITOR_PLUGIN_H