diff --git a/ChangeLog b/ChangeLog
index 43074d25e2..bf12b89631 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sun Dec 13 11:47:35 2015  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* object.c (rb_inspect): check the default internal encoding as
+	  String#inspect do.
+	  [ruby-dev:49415] [Bug #11787]
+
 Sun Dec 13 11:38:12 2015  Akinori MUSHA  <knu@iDaemons.org>
 
 	* lib/shellwords.rb: Turn on frozen-string-literal after fixing
diff --git a/object.c b/object.c
index 3111701c58..99f58a8f6c 100644
--- a/object.c
+++ b/object.c
@@ -467,22 +467,23 @@ rb_any_to_s(VALUE obj)
 
 VALUE rb_str_escape(VALUE str);
 /*
- * If the default external encoding is ASCII compatible, the encoding of
- * the inspected result must be compatible with it.
- * If the default external encoding is ASCII incompatible,
+ * If the default internal or external encoding is ASCII compatible,
+ * the encoding of the inspected result must be compatible with it.
+ * If the default internal or external encoding is ASCII incompatible,
  * the result must be ASCII only.
  */
 VALUE
 rb_inspect(VALUE obj)
 {
     VALUE str = rb_obj_as_string(rb_funcallv(obj, id_inspect, 0, 0));
-    rb_encoding *ext = rb_default_external_encoding();
-    if (!rb_enc_asciicompat(ext)) {
+    rb_encoding *enc = rb_default_internal_encoding();
+    if (enc == NULL) enc = rb_default_external_encoding();
+    if (!rb_enc_asciicompat(enc)) {
 	if (!rb_enc_str_asciionly_p(str))
 	    return rb_str_escape(str);
 	return str;
     }
-    if (rb_enc_get(str) != ext && !rb_enc_str_asciionly_p(str))
+    if (rb_enc_get(str) != enc && !rb_enc_str_asciionly_p(str))
 	return rb_str_escape(str);
     return str;
 }
diff --git a/test/ruby/test_m17n.rb b/test/ruby/test_m17n.rb
index 2e9e65b52f..4efe18187b 100644
--- a/test/ruby/test_m17n.rb
+++ b/test/ruby/test_m17n.rb
@@ -1648,4 +1648,17 @@ class TestM17N < Test::Unit::TestCase
     assert_match(escape_plain, 0x5b.chr(::Encoding::UTF_8), bug10670)
     assert_match(escape_plain, 0x5b.chr, bug10670)
   end
+
+  def test_inspect_with_default_internal
+    bug11787 = '[ruby-dev:49415] [Bug #11787]'
+
+    orig_int = Encoding.default_internal
+    Encoding.default_internal = ::Encoding::EUC_JP
+    s = begin
+          [e("\xB4\xC1\xBB\xFA")].inspect
+        ensure
+          Encoding.default_internal = orig_int
+        end
+    assert_equal(e("[\"\xB4\xC1\xBB\xFA\"]"), s, bug11787)
+  end
 end