diff --git a/smithy-aws-protocol-tests/model/restJson1/json-maps.smithy b/smithy-aws-protocol-tests/model/restJson1/json-maps.smithy
index 1d3c8ad4d65..e9b274a4576 100644
--- a/smithy-aws-protocol-tests/model/restJson1/json-maps.smithy
+++ b/smithy-aws-protocol-tests/model/restJson1/json-maps.smithy
@@ -133,6 +133,7 @@ structure JsonMapsInputOutput {
     myMap: JsonMapsInputOutputMap,
 }
 
+@sparse
 map JsonMapsInputOutputMap {
     key: String,
     value: GreetingStruct