diff --git a/ChangeLog b/ChangeLog
index c6f4435d11..b23d8317c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sun Jul 10 19:33:47 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* test/ruby/enc/test_case_comprehensive.rb: Changed testing logic in to
+	  catch unintended modifications of characters that do not have a case
+	  equivalent in the respective encoding.
+	* enc/iso_8859_1.c, enc/iso_8859_15.c: Fixed unintended modifications of
+	  micro sign and y with diaeresis.
+
 Sun Jul 10 17:05:36 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
 
 	* enc/iso_8859_4.c, test/ruby/enc/test_case_comprehensive.rb:
diff --git a/enc/iso_8859_1.c b/enc/iso_8859_1.c
index d12a8dfc51..ad3d4a531a 100644
--- a/enc/iso_8859_1.c
+++ b/enc/iso_8859_1.c
@@ -279,7 +279,7 @@ case_map (OnigCaseFoldType* flagP, const OnigUChar** pp,
 	code = 's';
       }
     }
-    else if (code==0xAA || code==0xBA) ;
+    else if (code==0xAA || code==0xBA || code==0xB5 || code==0xFF) ;
     else if ((EncISO_8859_1_CtypeTable[code] & BIT_CTYPE_UPPER)
 	     && (flags & (ONIGENC_CASE_DOWNCASE|ONIGENC_CASE_FOLD))) {
       flags |= ONIGENC_CASE_MODIFIED;
diff --git a/enc/iso_8859_15.c b/enc/iso_8859_15.c
index 066a08c9fb..5180383331 100644
--- a/enc/iso_8859_15.c
+++ b/enc/iso_8859_15.c
@@ -244,7 +244,7 @@ case_map (OnigCaseFoldType* flagP, const OnigUChar** pp,
 	code = 's';
       }
     }
-    else if (code==0xAA || code==0xBA) ;
+    else if (code==0xAA || code==0xBA || code==0xB5) ;
     else if ((EncISO_8859_15_CtypeTable[code] & BIT_CTYPE_UPPER)
 	     && (flags & (ONIGENC_CASE_DOWNCASE|ONIGENC_CASE_FOLD))) {
       flags |= ONIGENC_CASE_MODIFIED;
diff --git a/test/ruby/enc/test_case_comprehensive.rb b/test/ruby/enc/test_case_comprehensive.rb
index bd30166de3..d1d1c3b282 100644
--- a/test/ruby/enc/test_case_comprehensive.rb
+++ b/test/ruby/enc/test_case_comprehensive.rb
@@ -165,7 +165,12 @@ class TestComprehensiveCaseFold
         codepoints.each do |code|
           begin
             source = code.encode(encoding) * 5
-            target = "#{test.first_data[code]}#{test.follow_data[code]*4}".encode(encoding)
+            begin
+              target = "#{test.first_data[code]}#{test.follow_data[code]*4}".encode(encoding)
+            rescue Encoding::UndefinedConversionError
+              raise if code =~ /i|I/ # special case for Turkic
+              target = source
+            end
             result = source.send(test.method_name, *test.attributes)
             assert_equal target, result,
               proc{"from #{code*5} (#{source.dump}) expected #{target.dump} but was #{result.dump}"}