diff --git a/t/99_stream_param_bug.t b/t/99_stream_param_bug.t
new file mode 100644
index 0000000000..eb2843c90e
--- /dev/null
+++ b/t/99_stream_param_bug.t
@@ -0,0 +1,106 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use Test::More;
+use lib 'auto-lib';
+use lib 'lib';
+
+# Test that JSON responses don't have _stream_param
+# and binary responses do have _stream_param
+
+# Test 1: Pinpoint responses should NOT have _stream_param
+# because they return JSON, not binary streams
+{
+    require Paws::Pinpoint::SendMessagesResponse;
+    ok(!Paws::Pinpoint::SendMessagesResponse->can('_stream_param'),
+       "Pinpoint::SendMessagesResponse should NOT have _stream_param (JSON response)");
+    
+    # Check all Pinpoint responses that have payloads
+    my @pinpoint_responses_with_payload = qw(
+        CreateAppResponse
+        CreateCampaignResponse
+        CreateSegmentResponse
+        DeleteAppResponse
+        GetAppResponse
+        SendMessagesResponse
+        SendUsersMessagesResponse
+        UpdateAppSettingsResponse
+    );
+    
+    for my $response (@pinpoint_responses_with_payload) {
+        my $class = "Paws::Pinpoint::$response";
+        eval "require $class";
+        if ($@) {
+            diag "Could not load $class: $@";
+            next;
+        }
+        ok(!$class->can('_stream_param'),
+           "$response should NOT have _stream_param (JSON response)");
+    }
+}
+
+# Test 2: S3 GetObject SHOULD have _stream_param
+# because it returns binary data
+# (Check the file directly to avoid trait loading issues)
+{
+    my $s3_file = 'auto-lib/Paws/S3/GetObjectOutput.pm';
+    if (-f $s3_file) {
+        my $content = do { local $/; open my $fh, '<', $s3_file or die $!; <$fh> };
+        my $has_stream_param = ($content =~ /class_has _stream_param/);
+        ok($has_stream_param,
+           "S3::GetObjectOutput SHOULD have _stream_param (binary response)");
+        
+        if ($content =~ /class_has _stream_param.*?default.*?['"](Body)['"]/) {
+            pass("S3::GetObjectOutput _stream_param should be 'Body'");
+        } else {
+            fail("S3::GetObjectOutput _stream_param should be 'Body'");
+        }
+    } else {
+        skip("S3 GetObjectOutput not generated", 2);
+    }
+}
+
+# Test 3: Lambda responses should NOT have _stream_param
+# even though they have payloads, because they return JSON
+{
+    eval { require Paws::Lambda::InvokeOutput };
+    unless ($@) {
+        ok(!Paws::Lambda::InvokeOutput->can('_stream_param'),
+           "Lambda::InvokeOutput should NOT have _stream_param (JSON response)");
+    }
+}
+
+# Test 4: Test the actual bug scenario
+# When a service returns JSON with a payload property,
+# it should still be parsed as JSON, not treated as a raw stream
+{
+    # Mock a response handler to demonstrate the bug
+    package MockResponseHandler;
+    
+    sub handle_response {
+        my ($class, $response_class, $json_content) = @_;
+        
+        if ($response_class->can('_stream_param')) {
+            # BUG: With _stream_param, the JSON is NOT parsed
+            # and is returned as a raw string
+            return "BUG: JSON not parsed, returned as raw string";
+        } else {
+            # CORRECT: Without _stream_param, JSON is parsed
+            return "OK: JSON properly parsed into data structure";
+        }
+    }
+    
+    package main;
+    
+    # Test with Pinpoint response
+    my $result = MockResponseHandler->handle_response(
+        'Paws::Pinpoint::SendMessagesResponse',
+        '{"MessageResponse": {"ApplicationId": "test"}}'
+    );
+    
+    is($result, "OK: JSON properly parsed into data structure",
+       "Pinpoint responses should have JSON parsed, not returned as raw string");
+}
+
+done_testing();
\ No newline at end of file
diff --git a/templates/restjson/callresult_class.tt b/templates/restjson/callresult_class.tt
index 7ad4397064..0ad793bb68 100644
--- a/templates/restjson/callresult_class.tt
+++ b/templates/restjson/callresult_class.tt
@@ -14,9 +14,15 @@ package [% c.api %]::[% c.shapename_for_operation_output(op_name) %];
   [%- IF (shape.members.$param_name.streaming == 1) %], traits => ['ParamInBody'][% stream_param = param_name %][% END %]
   [%- IF (c.required_in_shape(shape,param_name)) %], required => 1[% END %]);
 [% END %]
+  [%- # Check if the payload member has streaming=1 (binary/blob data)
+      # Don't add _stream_param for regular JSON payloads like Pinpoint
+  -%]
   [%- IF (shape.payload) -%]
+    [%- payload_member = shape.members.item(shape.payload) -%]
+    [%- IF (payload_member.streaming == 1) -%]
   use MooseX::ClassAttribute;
-  class_has _stream_param => (is => 'ro', default => '[% c.to_payload_shape_name(shape.payload) %]');
+  class_has _stream_param => (is => 'ro', default => '[% shape.payload %]');
+    [%- END -%]
   [%- END %]
   has _request_id => (is => 'ro', isa => 'Str');
 [%- END %]