diff --git a/modules/aws-http4s/src/smithy4s/aws/AwsClient.scala b/modules/aws-http4s/src/smithy4s/aws/AwsClient.scala
index d39345427..3d36f56a4 100644
--- a/modules/aws-http4s/src/smithy4s/aws/AwsClient.scala
+++ b/modules/aws-http4s/src/smithy4s/aws/AwsClient.scala
@@ -71,7 +71,11 @@ object AwsClient {
 
       def baseRequest(endpoint: OperationSchema[_, _, _, _, _]): F[HttpRequest[Blob]] = {
         awsEnv.region.map { region =>
-          val endpointPrefix = awsService.endpointPrefix.getOrElse(endpoint.id.name)
+          val endpointPrefix =
+            awsService.endpointPrefix
+              .orElse(awsService.arnNamespace.map(_.value))
+              .getOrElse(endpoint.id.name)
+
           val baseUri = HttpUri(
             scheme = HttpUriScheme.Https,
             host = s"$endpointPrefix.$region.amazonaws.com",
diff --git a/modules/aws-http4s/src/smithy4s/aws/internals/AwsSigning.scala b/modules/aws-http4s/src/smithy4s/aws/internals/AwsSigning.scala
index 21f55f007..6ead1d101 100644
--- a/modules/aws-http4s/src/smithy4s/aws/internals/AwsSigning.scala
+++ b/modules/aws-http4s/src/smithy4s/aws/internals/AwsSigning.scala
@@ -60,7 +60,10 @@ private[aws] object AwsSigning {
   ): Client[F] => Client[F] = {
     val endpointPrefix = serviceHints
       .get(_root_.aws.api.Service)
-      .flatMap(_.endpointPrefix)
+      .flatMap { awsService =>
+        awsService.endpointPrefix
+          .orElse(awsService.arnNamespace.map(_.value))
+      }
       .getOrElse(serviceId.name)
       .toLowerCase()