diff --git a/lib/reporters/html.js b/lib/reporters/html.js
index f0fb538a91..034fb07f01 100644
--- a/lib/reporters/html.js
+++ b/lib/reporters/html.js
@@ -181,7 +181,7 @@ function HTML(runner, options) {
if (indexOfMessage === -1) {
stackString = test.err.stack;
} else {
- stackString = test.err.stack.substr(
+ stackString = test.err.stack.slice(
test.err.message.length + indexOfMessage
);
}