diff --git a/tests/checks/string-advanced.fish b/tests/checks/string-advanced.fish
new file mode 100644
index 000000000..22102f776
--- /dev/null
+++ b/tests/checks/string-advanced.fish
@@ -0,0 +1,3 @@
+#RUN: %fish --features regex-easyesc %s
+string replace -r 'a(.*)' '\U$0\E' abc
+# CHECK: ABC