diff --git a/src/filter/FeatureFilter.ts b/src/filter/FeatureFilter.ts
index 046cbe4..f31f5cd 100644
--- a/src/filter/FeatureFilter.ts
+++ b/src/filter/FeatureFilter.ts
@@ -3,7 +3,7 @@
 
 export interface IFeatureFilter {
     name: string; // e.g. Microsoft.TimeWindow
-    evaluate(context?: IFeatureFilterEvaluationContext, appContext?: unknown): Promise<boolean> | boolean;
+    evaluate(context: IFeatureFilterEvaluationContext, appContext?: unknown): Promise<boolean> | boolean;
 }
 
 export interface IFeatureFilterEvaluationContext {