diff --git a/lldb/source/Commands/CommandObjectSource.cpp b/lldb/source/Commands/CommandObjectSource.cpp
index 3c40849..63d319ee 100644
--- a/lldb/source/Commands/CommandObjectSource.cpp
+++ b/lldb/source/Commands/CommandObjectSource.cpp
@@ -231,8 +231,20 @@
         CommandObject (interpreter,
                        "source list",
                        "Display source code (as specified) based on the current executable's debug info.",
-                       "source list [<cmd-options>] [<filename>]")
+                        NULL)
     {
+        CommandArgumentEntry arg;
+        CommandArgumentData file_arg;
+        
+        // Define the first (and only) variant of this arg.
+        file_arg.arg_type = eArgTypeFilename;
+        file_arg.arg_repetition = eArgRepeatOptional;
+        
+        // There is only one variant this argument could be; put it into the argument entry.
+        arg.push_back (file_arg);
+        
+        // Push the data for the first argument into the m_arguments vector.
+        m_arguments.push_back (arg);
     }
 
     ~CommandObjectSourceList ()