diff --git a/crates/wiggle/tests/wasi.rs b/crates/wiggle/tests/wasi.rs
index 45e2b7d1ba..07b56db62a 100644
--- a/crates/wiggle/tests/wasi.rs
+++ b/crates/wiggle/tests/wasi.rs
@@ -16,8 +16,10 @@ wiggle::from_witx!({
 #[test]
 fn document_equivalent() {
     let macro_doc = metadata::document();
-    let disk_doc =
-        witx::load(&["$CARGO_MANIFEST_DIR/tests/wasi.witx"]).expect("load wasi.witx from disk");
+    let mut path = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    path.push("tests");
+    path.push("wasi.witx");
+    let disk_doc = witx::load(&[path]).expect("load wasi.witx from disk");
 
     assert_eq!(macro_doc, disk_doc);
 }