diff --git a/src/panels/lovelace/cards/hui-calendar-card.ts b/src/panels/lovelace/cards/hui-calendar-card.ts
index f72815c5f2..e6ad8abdf1 100644
--- a/src/panels/lovelace/cards/hui-calendar-card.ts
+++ b/src/panels/lovelace/cards/hui-calendar-card.ts
@@ -94,10 +94,12 @@ export class HuiCalendarCard extends LitElement implements LovelaceCard {
       (changedProps.has("_config") && this._config?.entities)
     ) {
       const computedStyles = getComputedStyle(this);
-      this._calendars = this._config!.entities.map((entity, idx) => ({
-        entity_id: entity,
-        backgroundColor: getColorByIndex(idx, computedStyles),
-      }));
+      if (this._config?.entities) {
+        this._calendars = this._config.entities.map((entity, idx) => ({
+          entity_id: entity,
+          backgroundColor: getColorByIndex(idx, computedStyles),
+        }));
+      }
     }
   }