diff --git a/projects/_shared/src/custom-shapes.ts b/projects/_shared/src/custom-shapes.ts
index c353041..de34d5e 100644
--- a/projects/_shared/src/custom-shapes.ts
+++ b/projects/_shared/src/custom-shapes.ts
@@ -1,4 +1,12 @@
-import {AbstractCanvas2D, ColorValue, EllipseShape, Rectangle, ShapeRegistry, RectangleShape} from '@maxgraph/core';
+import {AbstractCanvas2D, EllipseShape, ShapeRegistry, RectangleShape} from '@maxgraph/core';
+
+// The renderer builds a registered shape with no argument, so these defaults cannot come from a constructor. They are
+// also derived from the style, so `resetStyles()` wipes them on every style change. Each one is therefore declared
+// twice, as a class field for the first render and in a `resetStyles()` override for every later change, which is why
+// it is a named constant rather than a literal.
+const RECTANGLE_STROKE_WIDTH = 3;
+const RECTANGLE_IS_ROUNDED = true; // force rounded shape
+const ELLIPSE_STROKE_WIDTH = 5;
 
 export const registerCustomShapes = (): void => {
   console.info('Registering custom shapes...');
@@ -8,9 +16,13 @@ export const registerCustomShapes = (): void => {
 };
 
 class CustomRectangleShape extends RectangleShape {
-  constructor(bounds: Rectangle, fill: ColorValue, stroke: ColorValue) {
-    super(bounds, fill, stroke, 3);
-    this.isRounded = true; // force rounded shape
+  override strokeWidth = RECTANGLE_STROKE_WIDTH;
+  override isRounded = RECTANGLE_IS_ROUNDED;
+
+  override resetStyles(): void {
+    super.resetStyles();
+    this.strokeWidth = RECTANGLE_STROKE_WIDTH;
+    this.isRounded = RECTANGLE_IS_ROUNDED;
   }
 
     override paintBackground(
@@ -37,8 +49,11 @@ class CustomRectangleShape extends RectangleShape {
 }
 
 class CustomEllipseShape extends EllipseShape {
-  constructor(bounds: Rectangle, fill: string, stroke: string) {
-    super(bounds, fill, stroke, 5);
+  override strokeWidth = ELLIPSE_STROKE_WIDTH;
+
+  override resetStyles(): void {
+    super.resetStyles();
+    this.strokeWidth = ELLIPSE_STROKE_WIDTH;
   }
 
     override paintVertexShape(