diff --git a/src/python/m5/main.py b/src/python/m5/main.py
index 9342ad0bd7..ab723951bf 100644
--- a/src/python/m5/main.py
+++ b/src/python/m5/main.py
@@ -143,7 +143,8 @@ def parse_options():
     option("--debug-end", metavar="TICK", type='int',
         help="End debug output at TICK")
     option("--debug-file", metavar="FILE", default="cout",
-        help="Sets the output file for debug [Default: %default]")
+        help="Sets the output file for debug. Append '.gz' to the name for it"
+              " to be compressed automatically [Default: %default]")
     option("--debug-ignore", metavar="EXPR", action='append', split=':',
         help="Ignore EXPR sim objects")
     option("--remote-gdb-port", type='int', default=7000,