diff --git a/src/core/linux/log.c b/src/core/linux/log.c
index 221890c..de9be14 100644
--- a/src/core/linux/log.c
+++ b/src/core/linux/log.c
@@ -42,20 +42,16 @@
 
 int use_syslog = 0;
 
-int default_log_writer(H3270 GNUC_UNUSED(*session), const char *module, int GNUC_UNUSED(rc), const char *fmt, va_list arg_ptr) {
+int default_log_writer(H3270 GNUC_UNUSED(*session), void GNUC_UNUSED(*userdata), const char *module, int GNUC_UNUSED(rc), const char *message) {
 #ifdef HAVE_SYSLOG
 	if(use_syslog) {
-		vsyslog(LOG_INFO, fmt, arg_ptr);
+		syslog(LOG_INFO, "%s: %s", module, message);
 	} else {
-		printf("%s:\t",module);
-		vprintf(fmt,arg_ptr);
-		printf("\n");
+		printf("%s %s\n", module, message);
 		fflush(stdout);
 	}
 #else
-	printf("%s:\t",module);
-	vprintf(fmt,arg_ptr);
-	printf("\n");
+	printf("%s %s\n", module, message);
 	fflush(stdout);
 #endif
 	return 0;
diff --git a/src/core/log.c b/src/core/log.c
index 2eef69c..081963f 100644
--- a/src/core/log.c
+++ b/src/core/log.c
@@ -51,8 +51,12 @@ LIB3270_LOG_HANDLER loghandler = default_log_writer;
 
 /*---[ Implementacao ]--------------------------------------------------------------------------------------*/
 
-static void write_log(const H3270 *session, const char *module, int rc, const char *fmt, va_list arg_ptr) {
+static void write_log(const H3270 *session, const char *module, int rc, const char *fmt, va_list args) {
 
+	// 'mount' message.
+	char *message = lib3270_vsprintf(fmt,args);
+
+	// Write log
 	if(session) {
 
 		if(session->log.file) {
@@ -72,9 +76,7 @@ static void write_log(const H3270 *session, const char *module, int rc, const ch
 				strftime(timestamp, 79, "%x %X", localtime(&ltime));
 		#endif // HAVE_LOCALTIME_R
 
-				fprintf(f,"%s %s\t",timestamp,module);
-				vfprintf(f,fmt,arg_ptr);
-				fprintf(f,"\n");
+				fprintf(f,"%s %s\t%s\n",timestamp,module,message);
 
 				fclose(f);
 
@@ -82,14 +84,16 @@ static void write_log(const H3270 *session, const char *module, int rc, const ch
 
 		}
 
-		session->log.handler(session,module ? module : LIB3270_STRINGIZE_VALUE_OF(PRODUCT_NAME),rc,fmt,arg_ptr);
+		session->log.handler(session,session->log.userdata,module ? module : LIB3270_STRINGIZE_VALUE_OF(PRODUCT_NAME),rc,message);
 
 	} else {
 
-		loghandler(session, (module ? module : LIB3270_STRINGIZE_VALUE_OF(PRODUCT_NAME)),rc,fmt,arg_ptr);
+		loghandler(session, NULL, (module ? module : LIB3270_STRINGIZE_VALUE_OF(PRODUCT_NAME)),rc,message);
 
 	}
 
+	lib3270_free(message);
+
 }
 
 LIB3270_EXPORT const char * lib3270_get_log_filename(const H3270 * hSession) {
diff --git a/src/core/session.c b/src/core/session.c
index d305f58..136463a 100644
--- a/src/core/session.c
+++ b/src/core/session.c
@@ -199,8 +199,8 @@ static int load(H3270 *session, const char GNUC_UNUSED(*filename)) {
 	return errno = ENOTSUP;
 }
 
-static int def_trace(const H3270 GNUC_UNUSED(*session), void GNUC_UNUSED(*userdata), const char *fmt, va_list args) {
-	vfprintf(stdout,fmt,args);
+static int def_trace(const H3270 GNUC_UNUSED(*session), void GNUC_UNUSED(*userdata), const char *message) {
+	printf("%s",message);
 	fflush(stdout);
 	return 0;
 }
diff --git a/src/core/trace_ds.c b/src/core/trace_ds.c
index ad4b776..9f2dbf6 100644
--- a/src/core/trace_ds.c
+++ b/src/core/trace_ds.c
@@ -73,6 +73,53 @@
 /* Statics */
 static void	wtrace(H3270 *session, const char *fmt, ...);
 
+static void write_trace(const H3270 *session, const char *fmt, va_list args) {
+
+	// 'mount' message.
+	char *message = lib3270_vsprintf(fmt,args);
+
+	if(session->trace.file) {
+
+		// Has log file. Use it if possible.
+		FILE *f = fopen(session->trace.file, "a");
+
+		if(f) {
+
+			time_t ltime = time(0);
+
+		   char timestamp[80];
+#ifdef HAVE_LOCALTIME_R
+			struct tm tm;
+			strftime(timestamp, 79, "%x %X", localtime_r(&ltime,&tm));
+#else
+			strftime(timestamp, 79, "%x %X", localtime(&ltime));
+#endif // HAVE_LOCALTIME_R
+
+			fprintf(f,"%s %s\n",timestamp,message);
+
+			fclose(f);
+
+		}
+
+	}
+
+	session->trace.handler(session,session->trace.userdata,message);
+
+	lib3270_free(message);
+
+}
+
+/**
+ * @brief Write to the trace file.
+ */
+static void wtrace(H3270 *session, const char *fmt, ...) {
+	va_list args;
+	va_start(args, fmt);
+	write_trace(session, fmt, args);
+	va_end(args);
+}
+
+
 /* display a (row,col) */
 const char * rcba(H3270 *hSession, int baddr) {
 	static char buf[48];
@@ -161,7 +208,7 @@ void trace_dsn(H3270 *session, const char *fmt, ...) {
 
 	/* print out message */
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session,fmt,args);
 	va_end(args);
 }
 
@@ -176,18 +223,7 @@ void trace_ssl(H3270 *session, const char *fmt, ...) {
 
 	/* print out message */
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
-	va_end(args);
-}
-
-
-/**
- * @brief Write to the trace file.
- */
-static void wtrace(H3270 *session, const char *fmt, ...) {
-	va_list args;
-	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -195,7 +231,7 @@ LIB3270_EXPORT void lib3270_write_trace(H3270 *session, const char *fmt, ...) {
 	va_list args;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -206,7 +242,7 @@ LIB3270_EXPORT void lib3270_write_dstrace(H3270 *session, const char *fmt, ...) 
 		return;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -217,7 +253,7 @@ LIB3270_EXPORT void lib3270_write_nettrace(H3270 *session, const char *fmt, ...)
 		return;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -228,7 +264,7 @@ LIB3270_EXPORT void lib3270_write_screen_trace(H3270 *session, const char *fmt, 
 		return;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -239,7 +275,7 @@ LIB3270_EXPORT void lib3270_write_event_trace(H3270 *session, const char *fmt, .
 		return;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
@@ -250,7 +286,7 @@ LIB3270_EXPORT void lib3270_trace_event(H3270 *session, const char *fmt, ...) {
 		return;
 
 	va_start(args, fmt);
-	session->trace.handler(session,session->trace.userdata,fmt, args);
+	write_trace(session, fmt, args);
 	va_end(args);
 }
 
diff --git a/src/core/windows/log.c b/src/core/windows/log.c
index 4b9d08b..f1c1213 100644
--- a/src/core/windows/log.c
+++ b/src/core/windows/log.c
@@ -41,10 +41,7 @@
 
 /*---[ Implement ]------------------------------------------------------------------------------------------*/
 
-int default_log_writer(H3270 GNUC_UNUSED(*session), const char *module, int rc, const char *fmt, va_list arg_ptr) {
-	lib3270_autoptr(char) msg = lib3270_vsprintf(fmt,arg_ptr);
-
-	debug("%s",msg);
+int default_log_writer(H3270 GNUC_UNUSED(*session), const char *module, int rc, const char *msg) {
 
 	if(hEventLog) {
 		lib3270_autoptr(char) username = lib3270_get_user_name();
diff --git a/src/include/internals.h b/src/include/internals.h
index 6e4fa14..b25e34a 100644
--- a/src/include/internals.h
+++ b/src/include/internals.h
@@ -635,6 +635,7 @@ struct _h3270 {
 	struct {
 		char *file; 		///< @brief Log file name (if set).
 		LIB3270_LOG_HANDLER handler;
+		void *userdata;
 	} log;
 
 	struct {
@@ -739,7 +740,7 @@ LIB3270_INTERNAL void clear_chr(H3270 *hSession, int baddr);
 LIB3270_INTERNAL unsigned char get_field_attribute(H3270 *session, int baddr);
 
 /// @brief Default log writer.
-LIB3270_INTERNAL int default_log_writer(H3270 *session, const char *module, int rc, const char *fmt, va_list arg_ptr);
+LIB3270_INTERNAL int default_log_writer(H3270 *session, void *dunno, const char *module, int rc, const char *message);
 
 /// @brief The active log handler.
 LIB3270_INTERNAL LIB3270_LOG_HANDLER loghandler;
diff --git a/src/include/lib3270/log.h b/src/include/lib3270/log.h
index a877281..04773c2 100644
--- a/src/include/lib3270/log.h
+++ b/src/include/lib3270/log.h
@@ -52,7 +52,7 @@
 extern "C" {
 #endif
 
-typedef int (*LIB3270_LOG_HANDLER)(const H3270 *, const char *, int, const char *, va_list);
+typedef int (*LIB3270_LOG_HANDLER)(const H3270 *, void *, const char *, int, const char *);
 
 LIB3270_EXPORT void	  lib3270_set_log_handler(H3270 *session, const LIB3270_LOG_HANDLER loghandler);
 LIB3270_EXPORT int	  lib3270_set_log_filename(H3270 * hSession, const char *name);
diff --git a/src/include/lib3270/trace.h b/src/include/lib3270/trace.h
index e2bbebb..89adcc4 100644
--- a/src/include/lib3270/trace.h
+++ b/src/include/lib3270/trace.h
@@ -45,7 +45,7 @@ extern "C" {
 #define LIB3270_AS_PRINTF(a,b) __attribute__((format(printf, a, b)))
 #endif
 
-typedef int (*LIB3270_TRACE_HANDLER)(const H3270 *, void *, const char *, va_list);
+typedef int (*LIB3270_TRACE_HANDLER)(const H3270 *, void *, const char *);
 
 /**
  * @brief Set trace filename.
diff --git a/src/testprogram/testprogram.c b/src/testprogram/testprogram.c
index b13256e..6a0c985 100644
--- a/src/testprogram/testprogram.c
+++ b/src/testprogram/testprogram.c
@@ -50,16 +50,6 @@
 
 const char *trace_file = "test.trace";
 
-static int write_trace(const H3270 GNUC_UNUSED(*session), void GNUC_UNUSED(*userdata), const char *fmt, va_list args) {
-	FILE *out = fopen(trace_file,"a");
-	if(out) {
-
-		vfprintf(out,fmt,args);
-		fclose(out);
-	}
-	return 0;
-}
-
 static void online_group_state_changed(H3270 GNUC_UNUSED(*hSession), void GNUC_UNUSED(*dunno)) {
 	printf("\n\n%s\n\n",__FUNCTION__);
 }
@@ -138,8 +128,7 @@ int main(int argc, char *argv[]) {
 			return 0;
 
 		case 't':
-			trace_file = optarg;
-			lib3270_set_trace_handler(h,write_trace,NULL);
+			lib3270_set_trace_filename(h,optarg);
 			lib3270_set_toggle(h,LIB3270_TOGGLE_DS_TRACE,1);
 			break;
 		}
--
libgit2 0.21.2