diff --git a/Refit/ApiResponse.cs b/Refit/ApiResponse.cs
index 5a5792564..daa6e803b 100644
--- a/Refit/ApiResponse.cs
+++ b/Refit/ApiResponse.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Net;
 using System.Net.Http;
 using System.Net.Http.Headers;
@@ -53,6 +54,11 @@ public ApiResponse(HttpResponseMessage response, T? content, RefitSettings setti
         
         public HttpContentHeaders? ContentHeaders => response.Content?.Headers;
         
+#if NET5_0_OR_GREATER
+        [MemberNotNullWhen(true, nameof(Content))]
+        [MemberNotNullWhen(true, nameof(ContentHeaders))]
+        [MemberNotNullWhen(false, nameof(Error))]
+#endif
         public bool IsSuccessStatusCode => response.IsSuccessStatusCode;
 
         public string? ReasonPhrase => response.ReasonPhrase;