diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -182,8 +182,10 @@
                                      epilog='''
     Help text and arguments for individual test script:''',
                                      formatter_class=argparse.ArgumentDefaultsHelpFormatter)
-    parser.add_argument('--combinedlogslen', '-c', type=int, default=0,
-                        help='print a combined log (of length n lines) from all test nodes and test framework to the console on failure.')
+    parser.add_argument('--combinedlogslen', '-c', type=int, default=0, metavar='n',
+                        help='On failure, print a log (of length n lines) to '
+                             'the console, combined from the test framework '
+                             'and all test nodes.')
     parser.add_argument('--coverage', action='store_true',
                         help='generate a basic coverage report for the RPC interface')
     parser.add_argument(