diff --git a/src/helpers/scopeTab.js b/src/helpers/scopeTab.js
index d152951b..1e24378a 100644
--- a/src/helpers/scopeTab.js
+++ b/src/helpers/scopeTab.js
@@ -1,5 +1,11 @@
 import findTabbable from "./tabbable";
 
+function getActiveElement(el = document) {
+  return el.activeElement.shadowRoot
+    ? getActiveElement(el.activeElement.shadowRoot)
+    : el.activeElement;
+}
+
 export default function scopeTab(node, event) {
   const tabbable = findTabbable(node);
 
@@ -14,19 +20,20 @@ export default function scopeTab(node, event) {
   const shiftKey = event.shiftKey;
   const head = tabbable[0];
   const tail = tabbable[tabbable.length - 1];
+  const activeElement = getActiveElement();
 
   // proceed with default browser behavior on tab.
   // Focus on last element on shift + tab.
-  if (node === document.activeElement) {
+  if (node === activeElement) {
     if (!shiftKey) return;
     target = tail;
   }
 
-  if (tail === document.activeElement && !shiftKey) {
+  if (tail === activeElement && !shiftKey) {
     target = head;
   }
 
-  if (head === document.activeElement && shiftKey) {
+  if (head === activeElement && shiftKey) {
     target = tail;
   }
 
@@ -57,7 +64,7 @@ export default function scopeTab(node, event) {
   // the focus
   if (!isSafariDesktop) return;
 
-  var x = tabbable.indexOf(document.activeElement);
+  var x = tabbable.indexOf(activeElement);
 
   if (x > -1) {
     x += shiftKey ? -1 : 1;
diff --git a/src/helpers/tabbable.js b/src/helpers/tabbable.js
index ff462c22..dc2d3d42 100644
--- a/src/helpers/tabbable.js
+++ b/src/helpers/tabbable.js
@@ -38,7 +38,11 @@ function visible(element) {
   let rootNode = element.getRootNode && element.getRootNode();
   while (parentElement) {
     if (parentElement === document.body) break;
-    if (rootNode && parentElement === rootNode) parentElement = rootNode.host;
+
+    // if we are not hidden yet, skip to checking outside the Web Component
+    if (rootNode && parentElement === rootNode)
+      parentElement = rootNode.host.parentNode;
+
     if (hidesContents(parentElement)) return false;
     parentElement = parentElement.parentNode;
   }
@@ -61,5 +65,14 @@ function tabbable(element) {
 }
 
 export default function findTabbableDescendants(element) {
-  return [].slice.call(element.querySelectorAll("*"), 0).filter(tabbable);
+  const descendants = [].slice
+    .call(element.querySelectorAll("*"), 0)
+    .reduce(
+      (finished, el) => [
+        ...finished,
+        ...(!el.shadowRoot ? [el] : findTabbableDescendants(el.shadowRoot))
+      ],
+      []
+    );
+  return descendants.filter(tabbable);
 }