diff --git a/GCDWebServer/Core/GCDWebServerResponse.h b/GCDWebServer/Core/GCDWebServerResponse.h
index 7ef7d91..2e1365b 100644
--- a/GCDWebServer/Core/GCDWebServerResponse.h
+++ b/GCDWebServer/Core/GCDWebServerResponse.h
@@ -33,7 +33,7 @@ NS_ASSUME_NONNULL_BEGIN
  *  The GCDWebServerBodyReaderCompletionBlock is passed by GCDWebServer to the
  *  GCDWebServerBodyReader object when reading data from it asynchronously.
  */
-typedef void (^GCDWebServerBodyReaderCompletionBlock)(NSData* data, NSError* _Nullable error);
+typedef void (^GCDWebServerBodyReaderCompletionBlock)(NSData* _Nullable data, NSError* _Nullable error);
 
 /**
  *  This protocol is used by the GCDWebServerConnection to communicate with