diff --git a/os_testr/subunit_trace.py b/os_testr/subunit_trace.py
index 003299f..315d850 100755
--- a/os_testr/subunit_trace.py
+++ b/os_testr/subunit_trace.py
@@ -120,6 +120,7 @@ def print_attachments(stream, test, all_channels=False):
             # indent attachment lines 4 spaces to make them visually
             # offset
             for line in detail.as_text().split('\n'):
+                line = line.encode('utf8')
                 stream.write("    %s\n" % line)