diff --git a/testing/geckodriver/rust-version b/testing/geckodriver/rust-version
new file mode 100644
index 000000000000..8441236b78c3
--- /dev/null
+++ b/testing/geckodriver/rust-version
@@ -0,0 +1 @@
+rustc 0.13.0-nightly (fac5a0767 2014-11-26 22:37:06 +0000)