diff --git a/Libraries/src/Amazon.Lambda.AspNetCoreServer/AbstractAspNetCoreFunction.cs b/Libraries/src/Amazon.Lambda.AspNetCoreServer/AbstractAspNetCoreFunction.cs
index cd77fd273..9ba95feb0 100644
--- a/Libraries/src/Amazon.Lambda.AspNetCoreServer/AbstractAspNetCoreFunction.cs
+++ b/Libraries/src/Amazon.Lambda.AspNetCoreServer/AbstractAspNetCoreFunction.cs
@@ -75,6 +75,7 @@ public abstract class AbstractAspNetCoreFunction<TREQUEST, TRESPONSE> : Abstract
             ["image/x-icon"] = ResponseContentEncoding.Base64,
             ["application/zip"] = ResponseContentEncoding.Base64,
             ["application/pdf"] = ResponseContentEncoding.Base64,
+            ["application/x-protobuf"] = ResponseContentEncoding.Base64,
         };
 
         // Defines a mapping from registered content encodings to the response encoding format