diff --git a/core/src/components/header/header.tsx b/core/src/components/header/header.tsx
index f9f59a4862..17376a2e56 100644
--- a/core/src/components/header/header.tsx
+++ b/core/src/components/header/header.tsx
@@ -129,7 +129,9 @@ export class Header implements ComponentInterface {
       cloneElement('ion-title');
       cloneElement('ion-back-button');
 
-      this.collapsibleMainHeader!.classList.add('header-collapse-main');
+      if (this.collapsibleMainHeader !== undefined) {
+        this.collapsibleMainHeader.classList.add('header-collapse-main');
+      }
     });
 
     this.collapsibleHeaderInitialized = true;