diff --git a/tabs/internal/tab.ts b/tabs/internal/tab.ts
index b7731dd3c..579c18422 100644
--- a/tabs/internal/tab.ts
+++ b/tabs/internal/tab.ts
@@ -35,6 +35,13 @@ export class Tab extends LitElement {
     setupHostAria(Tab);
   }
 
+  /**
+   * Indicates that the element is a tab for `<md-tabs>`. Useful when
+   * clients implement their own custom `md-tab` components.
+   * @nocollapse
+   */
+  static readonly isTab = true;
+
   /**
    * Whether or not the tab is selected.
    **/
diff --git a/tabs/internal/tabs.ts b/tabs/internal/tabs.ts
index 8fa166689..be45d7b28 100644
--- a/tabs/internal/tabs.ts
+++ b/tabs/internal/tabs.ts
@@ -307,5 +307,6 @@ export class Tabs extends LitElement {
 }
 
 function isTab(element: unknown): element is Tab {
-  return element instanceof Tab;
+  if (!element) return false;
+  return 'isTab' in element.constructor && element.constructor.isTab === true;
 }