diff --git a/common/JackClient.h b/common/JackClient.h
index 26c50d78..17ec12e4 100644
--- a/common/JackClient.h
+++ b/common/JackClient.h
@@ -50,7 +50,8 @@ typedef void (*JackShutdownCallback)(void *arg);
 
 class JackClient : public JackClientInterface, public JackRunnableInterface
 {
-
+	friend class JackDebugClient;
+	
     protected:
 
         JackProcessCallback fProcess;
diff --git a/common/JackDebugClient.cpp b/common/JackDebugClient.cpp
index ec3cbae8..c9f1749c 100644
--- a/common/JackDebugClient.cpp
+++ b/common/JackDebugClient.cpp
@@ -18,7 +18,9 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
 
 #include "JackDebugClient.h"
+#include "JackEngineControl.h"
 #include "JackError.h"
+#include "JackTime.h"
 #include <iostream>
 #include <iomanip>
 #include <sstream>
@@ -438,10 +440,24 @@ void JackDebugClient::OnShutdown(JackShutdownCallback callback, void *arg)
     fClient->OnShutdown(callback, arg);
 }
 
+int JackDebugClient::TimeCallback(jack_nframes_t nframes, void *arg)
+{
+	JackDebugClient* client = (JackDebugClient*)arg;
+	jack_time_t t1 = GetMicroSeconds(); 
+	int res = client->fProcessTimeCallback(nframes, client->fProcessTimeCallbackArg);
+	jack_time_t t2 = GetMicroSeconds(); 
+	long delta = long((t2 - t1) - client->GetEngineControl()->fPeriodUsecs);
+	if (delta > 0) 
+		*client->fStream << "!!! ERROR !!! : XRun of " << delta << " us" << endl;
+	return res;
+}
+
 int JackDebugClient::SetProcessCallback(JackProcessCallback callback, void *arg)
 {
 	CheckClient();
-    return fClient->SetProcessCallback(callback, arg);
+	fProcessTimeCallback = callback;
+	fProcessTimeCallbackArg = arg;
+	return  fClient->SetProcessCallback(TimeCallback, this);
 }
 
 int JackDebugClient::SetXRunCallback(JackXRunCallback callback, void *arg)
diff --git a/common/JackDebugClient.h b/common/JackDebugClient.h
index ab08d1e9..bde079f8 100644
--- a/common/JackDebugClient.h
+++ b/common/JackDebugClient.h
@@ -45,23 +45,22 @@ PortFollower;
 /*!
 \brief A "decorator" debug client to validate API use.
 */
-
+ 
 class JackDebugClient : public JackClient
 {
-    private:
-
-        JackClient* fClient;
-        std::ofstream* fStream;
-
     protected:
 	
-        PortFollower fPortList[MAX_PORT_HISTORY]; // Arbitrary value... To be tuned...
+		JackClient* fClient;
+        std::ofstream* fStream;
+	      PortFollower fPortList[MAX_PORT_HISTORY]; // Arbitrary value... To be tuned...
         int fTotalPortNumber;	// The total number of port opened and maybe closed. Historical view.
         int fOpenPortNumber;	// The current number of opened port.
         int fIsActivated;
         int fIsDeactivated;
         int fIsClosed;
         char fClientName[JACK_CLIENT_NAME_SIZE];
+		JackProcessCallback fProcessTimeCallback;
+		void* fProcessTimeCallbackArg;
 
     public:
 
@@ -131,9 +130,9 @@ class JackDebugClient : public JackClient
 		jack_nframes_t Wait(int status);
 		
         JackClientControl* GetClientControl() const;
-		
 		void CheckClient() const;
-
+		
+		static int JackDebugClient::TimeCallback(jack_nframes_t nframes, void *arg);
 };