diff --git a/src/components/accordion-item/accordion-item.scss b/src/components/accordion-item/accordion-item.scss
index 1a5a0c9b07123c8ace4ebf97e0e2f166a1f247bf..cedea9e20d95c1e77c210ccda0dd3710471bd6b3 100644
--- a/src/components/accordion-item/accordion-item.scss
+++ b/src/components/accordion-item/accordion-item.scss
@@ -104,6 +104,21 @@
     span {
       text-align: left;
     }
+
+    // When accordion item is open.
+    &[aria-expanded='true'] {
+      position: relative;
+
+      &:after {
+        background: linear-gradient(to right, var(--grayscale-medium), var(--grayscale-white));
+        bottom: 0;
+        content: '';
+        height: 2px;
+        left: 0;
+        position: absolute;
+        width: 100%;
+      }
+    }
   }
 
   .hy-accordion--heading__icon {