diff --git a/test/ruby/test_hash.rb b/test/ruby/test_hash.rb
index 91423f81ea..83d16d462e 100644
--- a/test/ruby/test_hash.rb
+++ b/test/ruby/test_hash.rb
@@ -304,6 +304,20 @@ class TestHash < Test::Unit::TestCase
     assert_equal before, ObjectSpace.count_objects[:T_STRING]
   end
 
+  def test_AREF_fstring_key_default_proc
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      h = Hash.new do |h, k|
+        k.frozen?
+      end
+
+      str = "foo"
+      refute str.frozen? # assumes this file is frozen_string_literal: false
+      refute h[str]
+      refute h["foo"]
+    end;
+  end
+
   def test_ASET_fstring_key
     a, b = {}, {}
     assert_equal 1, a["abc"] = 1
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 2ff48d2662..2c0a369a43 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -5458,7 +5458,8 @@ vm_opt_aref_with(VALUE recv, VALUE key)
 {
     if (!SPECIAL_CONST_P(recv) && RBASIC_CLASS(recv) == rb_cHash &&
         BASIC_OP_UNREDEFINED_P(BOP_AREF, HASH_REDEFINED_OP_FLAG) &&
-        rb_hash_compare_by_id_p(recv) == Qfalse) {
+        rb_hash_compare_by_id_p(recv) == Qfalse &&
+        !FL_TEST(recv, RHASH_PROC_DEFAULT)) {
         return rb_hash_aref(recv, key);
     }
     else {