--- old/src/jdk.jshell/share/classes/jdk/internal/jshell/tool/JShellTool.java	2016-07-15 00:13:44.074659836 -0700
+++ new/src/jdk.jshell/share/classes/jdk/internal/jshell/tool/JShellTool.java	2016-07-15 00:13:43.984657557 -0700
@@ -105,6 +105,7 @@
 import static java.util.stream.Collectors.toMap;
 import static jdk.internal.jshell.debug.InternalDebugControl.DBG_COMPA;
 import static jdk.internal.jshell.debug.InternalDebugControl.DBG_DEP;
+import static jdk.internal.jshell.debug.InternalDebugControl.DBG_EC;
 import static jdk.internal.jshell.debug.InternalDebugControl.DBG_EVNT;
 import static jdk.internal.jshell.debug.InternalDebugControl.DBG_FMGR;
 import static jdk.internal.jshell.debug.InternalDebugControl.DBG_GEN;
@@ -1375,7 +1376,7 @@
     boolean cmdDebug(String arg) {
         if (arg.isEmpty()) {
             debug = !debug;
-            InternalDebugControl.setDebugFlags(state, debug ? DBG_GEN : 0);
+            InternalDebugControl.setDebugFlags(state, debug ? DBG_GEN | DBG_EC : 0);
             fluff("Debugging %s", debug ? "on" : "off");
         } else {
             int flags = 0;
@@ -1394,6 +1395,10 @@
                         flags |= DBG_GEN;
                         fluff("General debugging on");
                         break;
+                    case 'x':
+                        flags |= DBG_EC;
+                        fluff("Execution control debugging on");
+                        break;
                     case 'f':
                         flags |= DBG_FMGR;
                         fluff("File manager debugging on");
@@ -1412,7 +1417,7 @@
                         break;
                     default:
                         hard("Unknown debugging option: %c", ch);
-                        fluff("Use: 0 r g f c d");
+                        fluff("Use: 0 r g x f c d");
                         return false;
                 }
             }