diff --git a/tests/by-util/test_expr.rs b/tests/by-util/test_expr.rs
index a286f2cf4..6ff37075e 100644
--- a/tests/by-util/test_expr.rs
+++ b/tests/by-util/test_expr.rs
@@ -108,6 +108,14 @@ fn test_index() {
         .args(&["index", "αbcdef", "α"])
         .succeeds()
         .stdout_only("1\n");
+    new_ucmd!()
+        .args(&["index", "αbc_δef", "δ"])
+        .succeeds()
+        .stdout_only("5\n");
+    new_ucmd!()
+        .args(&["index", "αbc_δef", "δf"])
+        .succeeds()
+        .stdout_only("5\n");
     new_ucmd!()
         .args(&["index", "αbcdef", "fb"])
         .succeeds()