diff --git a/dim-testsuite/runtest.py b/dim-testsuite/runtest.py
index a49f893..8069528 100755
--- a/dim-testsuite/runtest.py
+++ b/dim-testsuite/runtest.py
@@ -161,11 +161,12 @@ def process_command(actual_output, expected_output, out, sort_before=False):
     if sort_before:
         actual_output.sort()
         expected_output.sort()
-    for actual, expected in zip_longest(actual_output, expected_output, fillvalue=''):
-        expected = expected.strip('\n')
-        if expected.endswith(' re'):
+    # output and expectation are bytes, like the rest of the file handling here
+    for actual, expected in zip_longest(actual_output, expected_output, fillvalue=b''):
+        expected = expected.strip(b'\n')
+        if expected.endswith(b' re'):
             if re.match(expected[:-3], actual):
-                out.write(expected + '\n')
+                out.write(expected + b'\n')
             else:
                 out.write(actual + b'\n')
                 passed = False
diff --git a/dim-testsuite/t/runtest-shell-output.t b/dim-testsuite/t/runtest-shell-output.t
new file mode 100644
index 0000000..33ed599
--- /dev/null
+++ b/dim-testsuite/t/runtest-shell-output.t
@@ -0,0 +1,10 @@
+# The test runner compares the output of shell lines (everything that does not
+# start with "ndcli") with the expected lines, exactly or as a regex when the
+# expectation ends with " re".
+$ echo hello
+hello
+$ printf 'one\ntwo\n'
+one
+two
+$ date +%Y
+^20[0-9][0-9]$ re