diff --git a/pytools/test/test_persistent_dict.py b/pytools/test/test_persistent_dict.py
index 884d926ebe452c068d6c1e4d6830319336874bba..f9450b6f80e016f3e408fa1f84f96ad45e92181b 100644
--- a/pytools/test/test_persistent_dict.py
+++ b/pytools/test/test_persistent_dict.py
@@ -746,11 +746,23 @@ def test_hash_function() -> None:
         return add_x
 
     f1 = get_fun(1)
+    f11 = get_fun(1)
     f2 = get_fun(2)
 
+    fa = get_fun
+    fb = get_fun
+
+    assert fa == fb
+    assert keyb(fa) == keyb(fb)
+
     assert f1 != f2
     assert keyb(f1) != keyb(f2)
 
+    # FIXME: inconsistency!
+    assert f1 != f11
+    assert hash(f1) != hash(f11)
+    assert keyb(f1) == keyb(f11)
+
     # }}}
 
     # {{{ local functions