diff --git a/smithy-aws-protocol-tests/model/restJson1/empty-input-output.smithy b/smithy-aws-protocol-tests/model/restJson1/empty-input-output.smithy
index 6f9ae7323c3..161707ec48a 100644
--- a/smithy-aws-protocol-tests/model/restJson1/empty-input-output.smithy
+++ b/smithy-aws-protocol-tests/model/restJson1/empty-input-output.smithy
@@ -83,7 +83,7 @@ apply EmptyInputAndEmptyOutput @httpRequestTests([
         protocol: restJson1,
         method: "POST",
         uri: "/EmptyInputAndEmptyOutput",
-        body: "{}",
+        body: "",
         bodyMediaType: "application/json"
     },
 ])
@@ -97,6 +97,14 @@ apply EmptyInputAndEmptyOutput @httpResponseTests([
         body: "",
         bodyMediaType: "application/json"
     },
+    {
+        id: "RestJsonEmptyInputAndEmptyJsonObjectOutput",
+        documentation: "Empty output serializes no payload",
+        protocol: restJson1,
+        code: 200,
+        body: "{}",
+        bodyMediaType: "application/json"
+    },
 ])
 
 structure EmptyInputAndEmptyOutputInput {}
diff --git a/smithy-aws-protocol-tests/model/restJson1/http-prefix-headers.smithy b/smithy-aws-protocol-tests/model/restJson1/http-prefix-headers.smithy
index 4cedb836bf2..860b5e4c55d 100644
--- a/smithy-aws-protocol-tests/model/restJson1/http-prefix-headers.smithy
+++ b/smithy-aws-protocol-tests/model/restJson1/http-prefix-headers.smithy
@@ -76,20 +76,6 @@ apply HttpPrefixHeaders @httpResponseTests([
             }
         }
     },
-    {
-        id: "RestJsonHttpPrefixHeadersAreNotPresent",
-        documentation: "No prefix headers are serialized because the value is empty",
-        protocol: restJson1,
-        code: 200,
-        body: "",
-        headers: {
-            "X-Foo": "Foo"
-        },
-        params: {
-            foo: "Foo",
-            fooMap: {}
-        }
-    },
 ])
 
 structure HttpPrefixHeadersInputOutput {