diff --git a/src/utils.js b/src/utils.js
index 85176b3b..ea59b235 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -420,7 +420,7 @@ function defaultGetLocalIdent(
       path.relative(context, `${dirname + path.sep}_`)
     );
 
-    directory = directory.substr(0, directory.length - 1);
+    directory = directory.substring(0, directory.length - 1);
 
     let folder = "";
 
diff --git a/test/helpers/readAsset.js b/test/helpers/readAsset.js
index fde3ff39..bd1ae276 100644
--- a/test/helpers/readAsset.js
+++ b/test/helpers/readAsset.js
@@ -10,7 +10,7 @@ export default (asset, compiler, stats) => {
   const queryStringIdx = targetFile.indexOf("?");
 
   if (queryStringIdx >= 0) {
-    targetFile = targetFile.substr(0, queryStringIdx);
+    targetFile = targetFile.slice(0, queryStringIdx);
   }
 
   try {