diff --git a/.travis.yml b/.travis.yml
index 6d0b82d1ca..5f513e7143 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,7 +9,7 @@ sudo: required
 env:
   global:
     - CRATE_NAME=nix
-    - CARGO_TEST_THREADS=1
+    - RUST_TEST_THREADS=1
 
 matrix:
   # These are all the build jobs. Adjust as necessary. Comment out what you
diff --git a/Cross.toml b/Cross.toml
new file mode 100644
index 0000000000..7c536dc5e7
--- /dev/null
+++ b/Cross.toml
@@ -0,0 +1,2 @@
+[build.env]
+passthrough = ["RUST_TEST_THREADS"]