diff --git a/test/tc_Stringprep.rb b/test/tc_Stringprep.rb
index c7f15cb..bcdd401 100644
--- a/test/tc_Stringprep.rb
+++ b/test/tc_Stringprep.rb
@@ -60,7 +60,7 @@ class Test_Stringprep < Test::Unit::TestCase
   def test_with_profile_STRINGPREP
     TESTCASES_STRINGPREP.each do |key, val|
       rc = Stringprep.with_profile(val[1], val[0])
-      assert_equal(val[2], rc, "TestCase #{key} failed")
+      assert_equal(val[2].force_encoding('ASCII-8BIT'), rc, "TestCase #{key} failed")
     end
   end
 
@@ -75,7 +75,7 @@ class Test_Stringprep < Test::Unit::TestCase
   def test_nfkc_normalize_NFKC
     TESTCASES_NFKC.each do |key, val|
       rc = Stringprep.nfkc_normalize(val[0])
-      assert_equal(val[1], rc, "TestCase #{key} failed")
+      assert_equal(val[1].force_encoding('ASCII-8BIT'), rc, "TestCase #{key} failed")
     end
   end
 end