diff --git a/package.json b/package.json
index 0e41d4c38a..958b782ac3 100644
--- a/package.json
+++ b/package.json
@@ -84,7 +84,7 @@
     "isomorphic-fetch": "^2.2.1",
     "linkifyjs": "^2.1.6",
     "lodash": "^4.17.14",
-    "lolex": "2.3.2",
+    "lolex": "4.2",
     "matrix-js-sdk": "github:matrix-org/matrix-js-sdk#develop",
     "optimist": "^0.6.1",
     "pako": "^1.0.5",
diff --git a/yarn.lock b/yarn.lock
index 4789b22041..ac1adf1d20 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4930,10 +4930,10 @@ loglevel@1.6.1:
   resolved "https://registry.yarnpkg.com/loglevel/-/loglevel-1.6.1.tgz#e0fc95133b6ef276cdc8887cdaf24aa6f156f8fa"
   integrity sha1-4PyVEztu8nbNyIh82vJKpvFW+Po=
 
-lolex@2.3.2:
-  version "2.3.2"
-  resolved "https://registry.yarnpkg.com/lolex/-/lolex-2.3.2.tgz#85f9450425103bf9e7a60668ea25dc43274ca807"
-  integrity sha512-A5pN2tkFj7H0dGIAM6MFvHKMJcPnjZsOMvR7ujCjfgW5TbV6H9vb1PgxLtHvjqNZTHsUolz+6/WEO0N1xNx2ng==
+lolex@4.2:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/lolex/-/lolex-4.2.0.tgz#ddbd7f6213ca1ea5826901ab1222b65d714b3cd7"
+  integrity sha512-gKO5uExCXvSm6zbF562EvM+rd1kQDnB9AZBbiQVzf1ZmdDpxUSvpnAaVOP83N/31mRK8Ml8/VE8DMvsAZQ+7wg==
 
 lolex@^2.4.2:
   version "2.7.5"