diff --git a/Library/Contributions/cmd/brew-test-bot.rb b/Library/Contributions/cmd/brew-test-bot.rb
index a9ad48ae2c..8ffa7998c7 100755
--- a/Library/Contributions/cmd/brew-test-bot.rb
+++ b/Library/Contributions/cmd/brew-test-bot.rb
@@ -522,7 +522,11 @@ if ARGV.include? "--junit"
       failure = testcase.add_element 'failure' if step.failed?
       if step.has_output?
         # Remove invalid XML CData characters from step output.
-        output = REXML::CData.new step.output.delete("\000\a\b\e\f")
+        output = step.output
+        if output.respond_to?(:force_encoding) && !output.valid_encoding?
+          output.force_encoding(Encoding::UTF_8)
+        end
+        output = REXML::CData.new output.delete("\000\a\b\e\f")
         if step.passed?
           system_out = testcase.add_element 'system-out'
           system_out.text = output