diff --git a/packages/grpc-native-core/index.d.ts b/packages/grpc-native-core/index.d.ts
index 4493f4b6..f548a5f0 100644
--- a/packages/grpc-native-core/index.d.ts
+++ b/packages/grpc-native-core/index.d.ts
@@ -443,7 +443,7 @@ declare module "grpc" {
    * unary responses.
    */
   type sendUnaryData<ResponseType> =
-    (error: ServiceError | null, value: ResponseType, trailer?: Metadata, flags?: number) => void;
+    (error: ServiceError | null, value: ResponseType | null, trailer?: Metadata, flags?: number) => void;
 
   /**
    * A class for storing metadata. Keys are normalized to lowercase ASCII.
@@ -1220,7 +1220,7 @@ declare module "grpc" {
    * @param value The response value, if the call succeeded
    */
   export type requestCallback<ResponseType> =
-    (error: ServiceError | null, value: ResponseType) => void;
+    (error: ServiceError | null, value: ResponseType | null) => void;
 
   /**
    * Return the underlying channel object for the specified client