diff --git a/lib/middleware/authentication.js b/lib/middleware/authentication.js
index ddbd6df4f..7e02b10d1 100644
--- a/lib/middleware/authentication.js
+++ b/lib/middleware/authentication.js
@@ -466,7 +466,7 @@ function getStringToSign(canonicalRequest) {
     ...canonicalRequest.amzHeaders,
     canonicalRequest.querystring
       ? `${canonicalRequest.uri}?${canonicalRequest.querystring}`
-      : canonicalRequest.uri,
+      : encodeURI(canonicalRequest.uri)
   ].join('\n');
 }