diff --git a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/endpointsV2/RuleSetParameterFinder.java b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/endpointsV2/RuleSetParameterFinder.java
index 1850952aa04..99678b75658 100644
--- a/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/endpointsV2/RuleSetParameterFinder.java
+++ b/smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/endpointsV2/RuleSetParameterFinder.java
@@ -28,6 +28,7 @@
 import software.amazon.smithy.model.shapes.OperationShape;
 import software.amazon.smithy.model.shapes.ServiceShape;
 import software.amazon.smithy.model.shapes.Shape;
+import software.amazon.smithy.model.shapes.ShapeType;
 import software.amazon.smithy.rulesengine.traits.ClientContextParamsTrait;
 import software.amazon.smithy.rulesengine.traits.ContextParamTrait;
 import software.amazon.smithy.rulesengine.traits.EndpointRuleSetTrait;
@@ -68,10 +69,22 @@ public Map<String, String> getClientContextParams() {
         if (trait.isPresent()) {
             ClientContextParamsTrait clientContextParamsTrait = trait.get();
             clientContextParamsTrait.getParameters().forEach((name, definition) -> {
-                map.put(
-                    name,
-                    definition.getType().toString().toLowerCase() // "boolean" and "string" are directly usable in TS.
-                );
+                ShapeType shapeType = definition.getType();
+                if (shapeType.isShapeType(ShapeType.STRING) || shapeType.isShapeType(ShapeType.BOOLEAN)) {
+                    map.put(
+                        name,
+                        definition.getType().toString().toLowerCase() // "boolean" and "string" are directly usable in TS.
+                    );
+                } else if (shapeType.isShapeType(ShapeType.LIST)) {
+                    map.put(
+                        name,
+                        "string[]" // Only string lists are supported.
+                    );
+                } else {
+                    throw new RuntimeException("unexpected type "
+                        + definition.getType().toString()
+                        + " received as clientContextParam.");
+                }
             });
         }
         return map;