1 files changed, 2 insertions, 1 deletions
diff --git a/test/lib/test/unit/assertions.rb b/test/lib/test/unit/assertions.rb
index d426a3d844..d23cd7220b 100644
--- a/test/lib/test/unit/assertions.rb
+++ b/test/lib/test/unit/assertions.rb
@@ -888,7 +888,8 @@ eom
           total = @count.to_s
           fmt = "%#{total.size}d"
           @failures.map {|k, (n, v)|
-            "\n#{i+=1}. [#{fmt%n}/#{total}] Assertion for #{k.inspect}\n#{v.message.b.gsub(/^/, '   | ')}"
+            v = v.message
+            "\n#{i+=1}. [#{fmt%n}/#{total}] Assertion for #{k.inspect}\n#{v.b.gsub(/^/, '   | ').force_encoding(v.encoding)}"
           }.join("\n")
         end