help="check src/mem/ruby/network/topologies for complete set")
     parser.add_option("--mesh-rows", type="int", default=1,
                       help="the number of rows in the mesh topology")
-    parser.add_option("--garnet-network", type="string", default=none,
+    parser.add_option("--garnet-network", type="string", default=None,
                       help="'fixed'|'flexible'")
 
     # ruby mapping options
-    parser.add_option("--numa-high-bit", type="int", default=none,
+    parser.add_option("--numa-high-bit", type="int", default=None,
                       help="high order address bit to use for numa mapping. " \
                            "0 = highest bit, not specified = lowest bit")