--- a/src/jdk.jcmd/share/classes/sun/tools/jcmd/Arguments.java	Tue May 29 11:20:04 2018 -0700
+++ b/src/jdk.jcmd/share/classes/sun/tools/jcmd/Arguments.java	Tue May 29 20:57:42 2018 +0200
@@ -88,7 +88,9 @@
         }
 
         if (listCounters != true && sb.length() == 0) {
-            throw new IllegalArgumentException("No command specified");
+            // Omitting the command shall cause the target VM to print out a list
+            // of available commands.
+            sb.append("help");
         }
 
         command = sb.toString().trim();