diff --git a/ChangeLog b/ChangeLog
index e8fa625051..d017319a41 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Wed May 25 08:01:39 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* enc/unicode.c: Fix flag error for switch from titlecase to lowercase.
+
+	* test/ruby/enc/test_case_mapping.rb: Tests for above error.
+
 Wed May 25 01:13:55 2016  Kazuki Yamaguchi  <k@rhe.jp>
 
 	* ext/openssl/ossl_pkey_ec.c (ec_key_new_from_group): Create a new
diff --git a/enc/unicode.c b/enc/unicode.c
index 8f978bc9a7..22d1dda809 100644
--- a/enc/unicode.c
+++ b/enc/unicode.c
@@ -670,6 +670,8 @@ onigenc_unicode_case_map(OnigCaseFoldType* flagP,
     OnigUChar *to_start = to;
     OnigCaseFoldType flags = *flagP;
     to_end -= CASE_MAPPING_SLACK;
+    /* copy flags ONIGENC_CASE_UPCASE     and ONIGENC_CASE_DOWNCASE over to
+     *            ONIGENC_CASE_UP_SPECIAL and ONIGENC_CASE_DOWN_SPECIAL */
     flags |= (flags&(ONIGENC_CASE_UPCASE|ONIGENC_CASE_DOWNCASE))<<ONIGENC_CASE_SPECIAL_OFFSET;
 
     while (*pp<end && to<=to_end) {
@@ -780,7 +782,8 @@ onigenc_unicode_case_map(OnigCaseFoldType* flagP,
 	to += ONIGENC_CODE_TO_MBC(enc, code, to);
 	/* switch from titlecase to lowercase for capitalize */
 	if (flags & ONIGENC_CASE_TITLECASE)
-	    flags ^= (ONIGENC_CASE_UPCASE|ONIGENC_CASE_TITLECASE|ONIGENC_CASE_DOWNCASE);
+	    flags ^= (ONIGENC_CASE_UPCASE    |ONIGENC_CASE_DOWNCASE|ONIGENC_CASE_TITLECASE|
+		      ONIGENC_CASE_UP_SPECIAL|ONIGENC_CASE_DOWN_SPECIAL);
     }
     *flagP = flags;
     return (int)(to-to_start);
diff --git a/test/ruby/enc/test_case_mapping.rb b/test/ruby/enc/test_case_mapping.rb
index 5fb7339eeb..2ef3360314 100644
--- a/test/ruby/enc/test_case_mapping.rb
+++ b/test/ruby/enc/test_case_mapping.rb
@@ -9,7 +9,8 @@ class TestCaseMappingPreliminary < Test::Unit::TestCase
   def check_upcase_properties(expected, start, *flags)
     assert_equal expected, start.upcase(*flags)
     temp = start.dup
-    assert_equal expected, temp.upcase!(*flags)
+    assert_equal expected, temp.upcase!(*flags) unless expected==temp
+    assert_equal nil, temp.upcase!(*flags) if expected==temp
     assert_equal expected, expected.upcase(*flags)
     temp = expected.dup
     assert_nil   temp.upcase!(*flags)
@@ -18,7 +19,8 @@ class TestCaseMappingPreliminary < Test::Unit::TestCase
   def check_downcase_properties(expected, start, *flags)
     assert_equal expected, start.downcase(*flags)
     temp = start.dup
-    assert_equal expected, temp.downcase!(*flags)
+    assert_equal expected, temp.downcase!(*flags) unless expected==temp
+    assert_equal nil, temp.downcase!(*flags) if expected==temp
     assert_equal expected, expected.downcase(*flags)
     temp = expected.dup
     assert_nil   temp.downcase!(*flags)
@@ -27,7 +29,8 @@ class TestCaseMappingPreliminary < Test::Unit::TestCase
   def check_capitalize_properties(expected, start, *flags)
     assert_equal expected, start.capitalize(*flags)
     temp = start.dup
-    assert_equal expected, temp.capitalize!(*flags)
+    assert_equal expected, temp.capitalize!(*flags) unless expected==temp
+    assert_equal nil, temp.capitalize!(*flags) if expected==temp
     assert_equal expected, expected.capitalize(*flags)
     temp = expected.dup
     assert_nil   temp.capitalize!(*flags)
@@ -64,8 +67,26 @@ class TestCaseMappingPreliminary < Test::Unit::TestCase
     check_swapcase_properties   'résumé DÜRST ĭñŧėřŊÃŢIJŇŐŃæłĩżàťïōņ', 'RÉSUMÉ dürst ĬÑŦĖŘŋãţijňőńÆŁĨŻÀŤÏŌŅ', :lithuanian
   end
 
+  def test_one_way_upcase
+    check_upcase_properties     'ΜΜΜΜΜ', 'µµµµµ', :lithuanian # MICRO SIGN -> Greek Mu
+    check_downcase_properties   'µµµµµ', 'µµµµµ', :lithuanian # MICRO SIGN -> Greek Mu
+    check_capitalize_properties 'Μµµµµ', 'µµµµµ', :lithuanian # MICRO SIGN -> Greek Mu
+    check_capitalize_properties 'Μµµµµ', 'µµµµµ', :turkic # MICRO SIGN -> Greek Mu
+    check_capitalize_properties 'H̱ẖẖẖẖ', 'ẖẖẖẖẖ', :lithuanian
+    check_capitalize_properties 'Βϐϐϐϐ', 'ϐϐϐϐϐ', :lithuanian
+    check_capitalize_properties 'Θϑϑϑϑ', 'ϑϑϑϑϑ', :lithuanian
+    check_capitalize_properties 'Φϕ', 'ϕϕ', :lithuanian
+    check_capitalize_properties 'Πϖ', 'ϖϖ', :lithuanian
+    check_capitalize_properties 'Κϰ', 'ϰϰ', :lithuanian
+    check_capitalize_properties 'Ρϱϱ', 'ϱϱϱ', :lithuanian
+    check_capitalize_properties 'Εϵ', 'ϵϵ', :lithuanian
+    check_capitalize_properties 'Ιͅͅͅͅ', 'ͅͅͅͅͅ', :lithuanian
+    check_capitalize_properties 'Sſſſſ', 'ſſſſſ', :lithuanian
+  end
+
   def test_various
     check_upcase_properties     'Μ', 'µ', :lithuanian # MICRO SIGN -> Greek Mu
+    check_downcase_properties   'µµµµµ', 'µµµµµ', :lithuanian # MICRO SIGN
     check_capitalize_properties 'Ss', 'ß', :lithuanian
     check_upcase_properties     'SS', 'ß', :lithuanian
   end