diff --git a/base/src/js_worker/types.rs b/base/src/js_worker/types.rs
new file mode 100644
index 000000000..14e3729d5
--- /dev/null
+++ b/base/src/js_worker/types.rs
@@ -0,0 +1,3 @@
+use std::collections::HashMap;
+
+pub type EnvVars = HashMap<String, String>;