diff --git a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/ServiceGenerator.java b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/ServiceGenerator.java
index 4d6d85cb221..6625a02fc9e 100644
--- a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/ServiceGenerator.java
+++ b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/ServiceGenerator.java
@@ -320,7 +320,7 @@ private void generateConstructor() {
 
                     String additionalParamsString = additionalParameters.isEmpty()
                             ? ""
-                            : ", " + String.join(", ", additionalParameters);
+                            : ", { " + String.join(", ", additionalParameters) + "}";
                     writer.write("let $L = $T($L$L);",
                                  generateConfigVariable(configVariable),
                                  plugin.getResolveFunction().get(),