diff --git a/src/objective-c/ProtoRPC/ProtoRPC.m b/src/objective-c/ProtoRPC/ProtoRPC.m
index a6c88488fc2..6085f893560 100644
--- a/src/objective-c/ProtoRPC/ProtoRPC.m
+++ b/src/objective-c/ProtoRPC/ProtoRPC.m
@@ -27,6 +27,24 @@
 #import <RxLibrary/GRXWriteable.h>
 #import <RxLibrary/GRXWriter+Transformations.h>
 
+/**
+  * Generate an NSError object that represents a failure in parsing a proto class.
+  */
+static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsingError) {
+  NSDictionary *info = @{
+                         NSLocalizedDescriptionKey : @"Unable to parse response from the server",
+                         NSLocalizedRecoverySuggestionErrorKey :
+                           @"If this RPC is idempotent, retry "
+                         @"with exponential backoff. Otherwise, query the server status before "
+                         @"retrying.",
+                         NSUnderlyingErrorKey : parsingError,
+                         @"Expected class" : expectedClass,
+                         @"Received value" : proto,
+                         };
+  // TODO(jcanizales): Use kGRPCErrorDomain and GRPCErrorCodeInternal when they're public.
+  return [NSError errorWithDomain:@"io.grpc" code:13 userInfo:info];
+}
+
 @implementation GRPCUnaryProtoCall {
   GRPCStreamingProtoCall *_call;
 }
@@ -201,7 +219,7 @@
     } else {
       if ([handler respondsToSelector:@selector(closedWithTrailingMetadata:error:)]) {
         dispatch_async(handler.dispatchQueue, ^{
-          [handler closedWithTrailingMetadata:nil error:error];
+          [handler closedWithTrailingMetadata:nil error:ErrorForBadProto(message, _responseClass, error)];
         });
       }
       _handler = nil;
@@ -232,21 +250,6 @@
 
 @end
 
-static NSError *ErrorForBadProto(id proto, Class expectedClass, NSError *parsingError) {
-  NSDictionary *info = @{
-    NSLocalizedDescriptionKey : @"Unable to parse response from the server",
-    NSLocalizedRecoverySuggestionErrorKey :
-        @"If this RPC is idempotent, retry "
-        @"with exponential backoff. Otherwise, query the server status before "
-        @"retrying.",
-    NSUnderlyingErrorKey : parsingError,
-    @"Expected class" : expectedClass,
-    @"Received value" : proto,
-  };
-  // TODO(jcanizales): Use kGRPCErrorDomain and GRPCErrorCodeInternal when they're public.
-  return [NSError errorWithDomain:@"io.grpc" code:13 userInfo:info];
-}
-
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-implementations"
 @implementation ProtoRPC {