diff --git a/test/lisp/subr-tests.el b/test/lisp/subr-tests.el
index 6df4a469326..be613ce7595 100644
--- a/test/lisp/subr-tests.el
+++ b/test/lisp/subr-tests.el
@@ -374,6 +374,8 @@
   (should-not (string-equal-ignore-case "abc" "abCD"))
   (should (string-equal-ignore-case "S" "s"))
   (should (string-equal-ignore-case "ẞ" "ß"))
+  (should (string-equal-ignore-case "Dz" "DZ"))
+  (should (string-equal-ignore-case "Όσος" "ΌΣΟΣ"))
   ;; not yet: (should (string-equal-ignore-case "SS" "ß"))
   ;; not yet: (should (string-equal-ignore-case "SS" "ẞ"))