diff --git a/ChangeLog b/ChangeLog
index 40f8edfff7..43ce833f06 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jun  6 17:29:35 2016  Martin Duerst  <duerst@it.aoyama.ac.jp>
+
+	* test/ruby/enc/test_case_comprehensive.rb: Speed up testing for small
+	  encodings by preselecting codepoints.
+
 Mon Jun  6 17:10:50 2016  Kazuki Yamaguchi  <k@rhe.jp>
 
 	* ext/openssl/ossl_cipher.c (ossl_cipher_free): Use EVP_CIPHER_CTX_free()
diff --git a/test/ruby/enc/test_case_comprehensive.rb b/test/ruby/enc/test_case_comprehensive.rb
index b0618eb663..3c15084cfb 100644
--- a/test/ruby/enc/test_case_comprehensive.rb
+++ b/test/ruby/enc/test_case_comprehensive.rb
@@ -99,11 +99,21 @@ class TestComprehensiveCaseFold < Test::Unit::TestCase
   end
 
   def self.generate_casefold_tests (encoding)
+    all_tests
+    # preselect codepoints to speed up testing for small encodings
+    codepoints = @@codepoints.select do |code|
+      begin
+        code.encode(encoding)
+        true
+      rescue Encoding::UndefinedConversionError
+        false
+      end
+    end
     all_tests.each do |test|
       attributes = test.attributes.map(&:to_s).join '-'
       attributes.prepend '_' unless attributes.empty?
       define_method "test_#{encoding}_#{test.method_name}#{attributes}" do
-        @@codepoints.each do |code|
+        codepoints.each do |code|
           begin
             source = code.encode(encoding) * 5
             target = test.first_data[code].encode(encoding) + test.follow_data[code].encode(encoding) * 4