diff --git a/lib/pen.js b/lib/pen.js
index aa70423..082d147 100644
--- a/lib/pen.js
+++ b/lib/pen.js
@@ -518,6 +518,8 @@ export default class Painter {
           this.ctx.fillText(text, x, y, measuredWith);
         }
         if (view.css.textDecoration) {
+          const fontSize = view.css.fontSize.toPx();
+          this.ctx.lineWidth = fontSize / 13;
           this.ctx.beginPath();
           this.ctx.moveTo(...this.callbackInfo.textDecoration.moveTo);
           this.ctx.lineTo(...this.callbackInfo.textDecoration.lineTo);
@@ -612,6 +614,7 @@ export default class Painter {
           }
           const fontSize = view.css.fontSize.toPx();
           if (view.css.textDecoration) {
+            this.ctx.lineWidth = fontSize / 13;
             this.ctx.beginPath();
             if (/\bunderline\b/.test(view.css.textDecoration)) {
               this.ctx.moveTo(lineX, y);