1 files changed, 6 insertions, 3 deletions
diff --git a/test/lib/test/unit/assertions.rb b/test/lib/test/unit/assertions.rb
index 9bb8686e1f..fda2299eb0 100644
--- a/test/lib/test/unit/assertions.rb
+++ b/test/lib/test/unit/assertions.rb
@@ -133,10 +133,13 @@ module Test
           raise TypeError, "Expected #{expected.inspect} to be a kind of String or Regexp, not #{expected.class}"
         end
 
-        ex = assert_raise(exception, msg || proc {"Exception(#{exception}) with message matches to #{expected.inspect}"}) do
-          yield
+        ex = m = nil
+        EnvUtil.with_default_internal(expected.encoding) do
+          ex = assert_raise(exception, msg || proc {"Exception(#{exception}) with message matches to #{expected.inspect}"}) do
+            yield
+          end
+          m = ex.message
         end
-        m = ex.message
         msg = message(msg, "") {"Expected Exception(#{exception}) was raised, but the message doesn't match"}
 
         if assert == :assert_equal