diff --git a/README.md b/README.md
index a4b0b189..e1bfee35 100755
--- a/README.md
+++ b/README.md
@@ -52,6 +52,7 @@ global manipulation. Our goal with **lab** is to keep the execution engine as si
     - `clover` - output results in [Clover XML](https://confluence.atlassian.com/display/CLOVER) format.
     - [Multiple Reporters](#multiple-reporters) - See Below
     - [Custom Reporters](#custom-reporters) - See Below
+- `-R`, `--rejections` - fail tests on unhandled Promise rejections.
 - `--shuffle` - randomize the order that test scripts are executed.  Will not work with `--id`.
 - `--seed` - use this seed to randomize the order with `--shuffle`. This is useful to debug order dependent test failures.
 - `-s`, `--silence` - silence test output, defaults to false.