diff --git a/editor/plugins/mesh_instance_editor_plugin.cpp b/editor/plugins/mesh_instance_editor_plugin.cpp
index cb5f7ba76c8..7ea2b27744c 100644
--- a/editor/plugins/mesh_instance_editor_plugin.cpp
+++ b/editor/plugins/mesh_instance_editor_plugin.cpp
@@ -344,6 +344,10 @@ void MeshInstanceEditor::_create_outline_mesh() {
 		err_dialog->set_text(TTR("Mesh has not surface to create outlines from!"));
 		err_dialog->popup_centered_minsize();
 		return;
+	} else if (mesh->get_surface_count() == 1 && mesh->surface_get_primitive_type(0) != Mesh::PRIMITIVE_TRIANGLES) {
+		err_dialog->set_text(TTR("Mesh primitive type is not PRIMITIVE_TRIANGLES!"));
+		err_dialog->popup_centered_minsize();
+		return;
 	}
 
 	Ref<Mesh> mesho = mesh->create_outline(outline_size->get_value());
diff --git a/scene/resources/mesh.cpp b/scene/resources/mesh.cpp
index 949ba12a4c7..b832ea12397 100644
--- a/scene/resources/mesh.cpp
+++ b/scene/resources/mesh.cpp
@@ -315,6 +315,8 @@ Ref<Mesh> Mesh::create_outline(float p_margin) const {
 		}
 	}
 
+	ERR_FAIL_COND_V(arrays.size() != ARRAY_MAX, Ref<ArrayMesh>());
+
 	{
 		PoolVector<int>::Write ir;
 		PoolVector<int> indices = arrays[ARRAY_INDEX];