Index: src/main/java/hudson/model/Computer.java
===================================================================
--- src/main/java/hudson/model/Computer.java	(revision 26224)
+++ src/main/java/hudson/model/Computer.java	(working copy)
@@ -615,6 +615,8 @@
      */
     @Exported
     public final boolean isIdle() {
+        if (!oneOffExecutors.isEmpty())
+            return false;
         for (Executor e : executors)
             if(!e.isIdle())
                 return false;