diff --git a/rbtree.c b/rbtree.c
index 51f8238..3095cd1 100644
--- a/rbtree.c
+++ b/rbtree.c
@@ -15,6 +15,10 @@
 #define RETURN_ENUMERATOR(obj, argc, argv) ((void)0)
 #endif
 
+#ifndef RHASH_SET_IFNONE
+#define RHASH_SET_IFNONE(h, ifnone) (RHASH_IFNONE(h) = ifnone)
+#endif
+
 #if !defined(RUBY_API_VERSION_CODE) || (RUBY_API_VERSION_CODE < 20700)
 #define HAVE_TAINT
 #endif
@@ -1084,6 +1088,7 @@ rbtree_to_hash(VALUE self)
 
     hash = rb_hash_new();
     rbtree_for_each(self, to_hash_i, (void*)hash);
+    RHASH_SET_IFNONE(hash, IFNONE(self));
     if (FL_TEST(self, RBTREE_PROC_DEFAULT))
         FL_SET(hash, HASH_PROC_DEFAULT);
 #ifdef HAVE_TAINT
diff --git a/test.rb b/test.rb
index 37a7db0..dc4715a 100644
--- a/test.rb
+++ b/test.rb
@@ -518,6 +518,15 @@ def test_to_hash
     @rbtree.default = "e"
     hash = @rbtree.to_hash
     assert_equal(@rbtree.to_a.flatten, hash.to_a.flatten)
+    assert_equal("e", hash.default)
+
+    rbtree = RBTree.new { "e" }
+    hash = rbtree.to_hash
+    if (hash.respond_to?(:default_proc))
+      assert_equal(rbtree.default_proc, hash.default_proc)
+    else
+      assert_equal(rbtree.default_proc, hash.default)
+    end
   end
 
   def test_to_rbtree