diff --git a/smithy-aws-protocol-tests/model/restJson1/http-headers.smithy b/smithy-aws-protocol-tests/model/restJson1/http-headers.smithy
index 62e6639cada..59642634cbb 100644
--- a/smithy-aws-protocol-tests/model/restJson1/http-headers.smithy
+++ b/smithy-aws-protocol-tests/model/restJson1/http-headers.smithy
@@ -112,7 +112,7 @@ apply InputAndOutputWithHeaders @httpRequestTests([
         method: "POST",
         uri: "/InputAndOutputWithHeaders",
         headers: {
-            "X-TimestampList": "\"Mon, 16 Dec 2019 23:48:18 GMT\", \"Mon, 16 Dec 2019 23:48:18 GMT\""
+            "X-TimestampList": "Mon, 16 Dec 2019 23:48:18 GMT, Mon, 16 Dec 2019 23:48:18 GMT"
         },
         body: "",
         params: {
@@ -261,7 +261,7 @@ apply InputAndOutputWithHeaders @httpResponseTests([
         protocol: restJson1,
         code: 200,
         headers: {
-            "X-TimestampList": "\"Mon, 16 Dec 2019 23:48:18 GMT\", \"Mon, 16 Dec 2019 23:48:18 GMT\""
+            "X-TimestampList": "Mon, 16 Dec 2019 23:48:18 GMT, Mon, 16 Dec 2019 23:48:18 GMT"
         },
         params: {
             headerTimestampList: [1576540098, 1576540098]