diff --git a/hassio/src/hassio-main.ts b/hassio/src/hassio-main.ts
index 7d55a23378..ccabb2e426 100644
--- a/hassio/src/hassio-main.ts
+++ b/hassio/src/hassio-main.ts
@@ -106,7 +106,9 @@ export class HassioMain extends urlSyncMixin(ProvideHassLitMixin(LitElement)) {
         };
       }
     } else {
-      themeName = (this.hass.selectedTheme as unknown) as string;
+      themeName =
+        ((this.hass.selectedTheme as unknown) as string) ||
+        this.hass.themes.default_theme;
     }
 
     applyThemesOnElement(