diff --git a/src/include/lib3270/session.h b/src/include/lib3270/session.h
index dd1073c..10f147d 100644
--- a/src/include/lib3270/session.h
+++ b/src/include/lib3270/session.h
@@ -79,7 +79,6 @@
 
 		void (*message)(H3270 *session, LIB3270_NOTIFY id , const char *title, const char *message, const char *text);
 		void (*popup)(H3270 *session, LIB3270_NOTIFY id, const char *title, const char *msg, const char *fmt, va_list);
-		void (*trace)(H3270 *session, const char *fmt, va_list args);
 
 #ifdef HAVE_LIBSSL
 		void (*set_peer_certificate)(const X509 *cert);
diff --git a/src/include/lib3270/trace.h b/src/include/lib3270/trace.h
index 0f337f9..eafedd8 100644
--- a/src/include/lib3270/trace.h
+++ b/src/include/lib3270/trace.h
@@ -42,18 +42,18 @@
 	#define LIB3270_AS_PRINTF(a,b) __attribute__((format(printf, a, b)))
 #endif
 
-	typedef void (*LIB3270_TRACE_HANDLER)(H3270 *, const char *, va_list);
+	typedef void (*LIB3270_TRACE_HANDLER)(H3270 *, void *, const char *, va_list);
 
 
 	/**
 	 * Set trace handle callback.
 	 *
-	 * @param handle	Callback to write in trace file or show trace window (NULL send all trace to stdout/syslog).
-	 * @param data		User data to pass to the trace handler.
+	 * @param hSession	TN3270 Session handle.
+	 * @param handler	Callback to write in trace file or show trace window (NULL send all trace to stdout/syslog).
+	 * @param userdata	User data to pass to the trace handler.
 	 *
-	 * @return Current trace handler
 	 */
-	LIB3270_EXPORT LIB3270_TRACE_HANDLER lib3270_set_trace_handler(H3270 *session, LIB3270_TRACE_HANDLER handler);
+	LIB3270_EXPORT void lib3270_set_trace_handler(H3270 *hSession, LIB3270_TRACE_HANDLER handler, void *userdata);
 
 	/**
 	 * Write on trace file.
diff --git a/src/lib3270/private.h b/src/lib3270/private.h
index 2cf7ba9..d276e86 100644
--- a/src/lib3270/private.h
+++ b/src/lib3270/private.h
@@ -618,6 +618,12 @@ struct _h3270
 	input_t 				* inputs;
 	int						  inputs_changed : 1;
 
+	// Trace Window.
+	struct {
+		void (*handler)(H3270 *session, void *userdata, const char *fmt, va_list args);
+		void *userdata;
+	} trace;
+
 	// Callbacks.
 	struct lib3270_state_callback		* st_callbacks[LIB3270_STATE_USER];
 	struct lib3270_state_callback		* st_last[LIB3270_STATE_USER];
diff --git a/src/lib3270/session.c b/src/lib3270/session.c
index b126c29..ae0a0f4 100644
--- a/src/lib3270/session.c
+++ b/src/lib3270/session.c
@@ -209,7 +209,7 @@ static void def_popup(H3270 *session, LIB3270_NOTIFY type unused, const char *ti
 #endif // ANDROID
 }
 
-static void def_trace(H3270 *session unused, const char *fmt, va_list args)
+static void def_trace(H3270 *session unused, void *userdata unused, const char *fmt, va_list args)
 {
 	vfprintf(stdout,fmt,args);
 	fflush(stdout);
@@ -271,7 +271,6 @@ static void lib3270_session_init(H3270 *hSession, const char *model, const char 
 	hSession->cbk.update_selection		= update_selection;
 	hSession->cbk.cursor 				= set_cursor;
 	hSession->cbk.message				= message;
-	hSession->cbk.trace					= def_trace;
 	hSession->cbk.popup					= def_popup;
 	hSession->cbk.update_ssl			= update_ssl;
 	hSession->cbk.display				= screen_disp;
@@ -282,6 +281,9 @@ static void lib3270_session_init(H3270 *hSession, const char *model, const char 
 	hSession->cbk.print					= print;
 	hSession->cbk.set_peer_certificate	= set_peer_certificate;
 
+	// Trace management.
+	hSession->trace.handler				= def_trace;
+
 	// Set the defaults.
 	hSession->extended  			=  1;
 	hSession->typeahead				=  1;
@@ -321,11 +323,12 @@ static void lib3270_session_init(H3270 *hSession, const char *model, const char 
 
 }
 
-LIB3270_EXPORT LIB3270_TRACE_HANDLER lib3270_set_trace_handler(H3270 *session, LIB3270_TRACE_HANDLER handler)
+LIB3270_EXPORT void lib3270_set_trace_handler(H3270 *hSession, LIB3270_TRACE_HANDLER handler, void *userdata)
 {
-	void (*ret)(H3270 *session, const char *fmt, va_list args) = session->cbk.trace;
-	session->cbk.trace = handler ? handler : def_trace;
-	return ret;
+	CHECK_SESSION_HANDLE(hSession);
+
+	hSession->trace.handler	= handler ? handler : def_trace;
+	hSession->trace.userdata	= userdata;
 }
 
 LIB3270_EXPORT void lib3270_set_popup_handler(H3270 *session, void (*handler)(H3270 *, LIB3270_NOTIFY, const char *, const char *, const char *, va_list)) {
diff --git a/src/lib3270/trace_ds.c b/src/lib3270/trace_ds.c
index e3116c0..233b0b1 100644
--- a/src/lib3270/trace_ds.c
+++ b/src/lib3270/trace_ds.c
@@ -170,7 +170,7 @@ void trace_dsn(H3270 *session, const char *fmt, ...)
 
 	/* print out message */
 	va_start(args, fmt);
-	session->cbk.trace(session,fmt, args);
+	session->trace.handler(session,session->trace.userdata,fmt, args);
 	va_end(args);
 }
 
@@ -179,7 +179,7 @@ static void wtrace(H3270 *session, const char *fmt, ...)
 {
 	va_list args;
 	va_start(args, fmt);
-	session->cbk.trace(session,fmt, args);
+	session->trace.handler(session,session->trace.userdata,fmt, args);
 	va_end(args);
 }
 
@@ -191,7 +191,7 @@ LIB3270_EXPORT void lib3270_write_dstrace(H3270 *session, const char *fmt, ...)
 		return;
 
 	va_start(args, fmt);
-	session->cbk.trace(session,fmt, args);
+	session->trace.handler(session,session->trace.userdata,fmt, args);
 	va_end(args);
 }
 
@@ -203,7 +203,7 @@ LIB3270_EXPORT void lib3270_write_nettrace(H3270 *session, const char *fmt, ...)
 		return;
 
 	va_start(args, fmt);
-	session->cbk.trace(session,fmt, args);
+	session->trace.handler(session,session->trace.userdata,fmt, args);
 	va_end(args);
 }
 
@@ -216,7 +216,7 @@ LIB3270_EXPORT void lib3270_trace_event(H3270 *session, const char *fmt, ...)
 		return;
 
 	va_start(args, fmt);
-	session->cbk.trace(session,fmt, args);
+	session->trace.handler(session,session->trace.userdata,fmt, args);
 	va_end(args);
 }
 
--
libgit2 0.21.2