diff --git a/service.js b/service.js
index 83e68b6..2858163 100644
--- a/service.js
+++ b/service.js
@@ -692,7 +692,9 @@ class BesService {
           const x2 = rect.right
           const y = rect.bottom
           const scale = (rect.bottom - rect.top) / 18
-          this.drawAttentionRequired(x1, x2, y, amplitude, scale)
+          if (ruleId !== 'MORFOLOGIK_RULE') {
+            this.drawDoubleUnderline(x1, x2, y, scale)
+          } else this.drawAttentionRequired(x1, x2, y, amplitude, scale)
         }
 
         markerY1 = Math.min(...match.highlights.map(rect => rect.top))
@@ -892,6 +894,23 @@ class BesService {
     this.ctx.stroke()
   }
 
+  /**
+   *
+   * @param {Number} x1 Sign left [px]
+   * @param {Number} x2 Sign right [px]
+   * @param {Number} y Sign baseline [px]
+   * @param {Number} scale Sign scale
+   */
+  drawDoubleUnderline(x1, x2, y, scale) {
+    const dpr = window.devicePixelRatio
+    this.ctx.beginPath()
+    this.ctx.moveTo(x1 * dpr, (y - 2 * scale) * dpr)
+    this.ctx.lineTo(x2 * dpr, (y - 2 * scale) * dpr)
+    this.ctx.moveTo(x1 * dpr, (y + 1 * scale) * dpr)
+    this.ctx.lineTo(x2 * dpr, (y + 1 * scale) * dpr)
+    this.ctx.stroke()
+  }
+
   /**
    * Sets markup font
    *