diff --git a/lib/region_config.js b/lib/region_config.js
index f401383d7f..2e8d0de628 100644
--- a/lib/region_config.js
+++ b/lib/region_config.js
@@ -63,7 +63,9 @@ function configureEndpoint(service) {
       }
 
       // signature version
-      if (!config.signatureVersion) config.signatureVersion = 'v4';
+      if (!config.signatureVersion) {
+        config.signatureVersion = (service.api && service.api.signatureVersion) || 'v4';
+      }
 
       // merge config
       applyConfig(service, config);