diff --git a/gems/bundled_gems b/gems/bundled_gems
index fcf63ab603ac6b..e709d57b793039 100644
--- a/gems/bundled_gems
+++ b/gems/bundled_gems
@@ -13,7 +13,7 @@ test-unit           3.7.7   https://github.com/test-unit/test-unit
 rexml               3.4.4   https://github.com/ruby/rexml
 rss                 0.3.2   https://github.com/ruby/rss
 net-ftp             0.3.9   https://github.com/ruby/net-ftp
-net-imap            0.6.2   https://github.com/ruby/net-imap
+net-imap            0.6.2   https://github.com/ruby/net-imap            d9ae35ef913a45f83387b8444cdce4fb1cbf01af
 net-pop             0.1.2   https://github.com/ruby/net-pop
 net-smtp            0.5.1   https://github.com/ruby/net-smtp
 matrix              0.4.3   https://github.com/ruby/matrix
diff --git a/struct.c b/struct.c
index 667d35424fb8d1..31df3798cbcb4b 100644
--- a/struct.c
+++ b/struct.c
@@ -1809,6 +1809,7 @@ rb_data_initialize_m(int argc, const VALUE *argv, VALUE self)
         if (num_members > 0) {
             rb_exc_raise(rb_keyword_error_new("missing", members));
         }
+        OBJ_FREEZE(self);
         return Qnil;
     }
     if (argc > 1 || !RB_TYPE_P(argv[0], T_HASH)) {
diff --git a/test/ruby/test_data.rb b/test/ruby/test_data.rb
index dd698fdcc4a30e..5ac4c6b84b66aa 100644
--- a/test/ruby/test_data.rb
+++ b/test/ruby/test_data.rb
@@ -262,6 +262,7 @@ def test_memberless
     assert_equal('#<data >', test.inspect)
     assert_equal([], test.members)
     assert_equal({}, test.to_h)
+    assert_predicate(test, :frozen?)
   end
 
   def test_dup