diff --git a/PluginCommon/PluginManager.cs b/PluginCommon/PluginManager.cs
index 0112c1b..5015584 100644
--- a/PluginCommon/PluginManager.cs
+++ b/PluginCommon/PluginManager.cs
@@ -39,6 +39,8 @@ namespace PluginCommon {
         /// </summary>
         private byte[] mFileData;
 
+        private DateTime mLastPing;
+
 
         /// <summary>
         /// Constructor, invoked from CreateInstanceAndUnwrap().
@@ -46,6 +48,8 @@ namespace PluginCommon {
         public PluginManager() {
             Debug.WriteLine("PluginManager ctor (id=" + AppDomain.CurrentDomain.Id + ")");
 
+            mLastPing = DateTime.Now;
+
             // Seems to require [SecurityCritical]
             //Type lsc = Type.GetType("System.Runtime.Remoting.Lifetime.LifetimeServices");
             //PropertyInfo prop = lsc.GetProperty("LeaseTime");
@@ -75,7 +79,9 @@ namespace PluginCommon {
         public int Ping(int val) {
             Debug.WriteLine("PluginManager Ping tid=" + Thread.CurrentThread.ManagedThreadId +
                 " (id=" + AppDomain.CurrentDomain.Id + "): " + val);
-            return val + 1;
+            int result = (int)(DateTime.Now - mLastPing).TotalSeconds;
+            mLastPing = DateTime.Now;
+            return result;
         }
 
         /// <summary>
diff --git a/SourceGen/Sandbox/DomainManager.cs b/SourceGen/Sandbox/DomainManager.cs
index a871dc3..813f2d8 100644
--- a/SourceGen/Sandbox/DomainManager.cs
+++ b/SourceGen/Sandbox/DomainManager.cs
@@ -84,9 +84,10 @@ namespace SourceGen.Sandbox {
                     // waits for the currently-executing timer event to finish.  So wrap
                     // everything in try/catch.
                     try {
-                        mPluginManager.Instance.Ping(0);
-                        //Debug.WriteLine("KeepAlive tid=" +
-                        //    System.Threading.Thread.CurrentThread.ManagedThreadId);
+                        int result = mPluginManager.Instance.Ping(1000);
+                        Debug.WriteLine("KeepAlive tid=" +
+                            System.Threading.Thread.CurrentThread.ManagedThreadId +
+                            " result=" + result);
                     } catch (Exception ex) {
                         Debug.WriteLine("Keep-alive timer failed: " + ex.Message);
                     }