diff --git a/src/support/Systemcall.cpp b/src/support/Systemcall.cpp
index f1db006a8e..b7f0355fc6 100644
--- a/src/support/Systemcall.cpp
+++ b/src/support/Systemcall.cpp
@@ -60,12 +60,15 @@ int Systemcall::startscript(Starttype how, string const & what)
 #else
 	QString cmd = QString::fromLocal8Bit(what.c_str());
 	QProcess * process = new QProcess;
-	if (os::terminal_output()) {
-		// Qt won't start the process if we redirect stdout and
-		// stderr this way, without running in a terminal.
+
+	// Qt won't start the process if we redirect stdout/stderr in
+	// this way and they are not connected to a terminal (maybe
+	// because we were launched from some desktop GUI).
+	if (os::is_terminal(os::STDOUT))
 		process->setStandardOutputFile(toqstr(os::stdoutdev()));
+	if (os::is_terminal(os::STDERR))
 		process->setStandardErrorFile(toqstr(os::stderrdev()));
-	}
+
 	process->start(cmd);
 	if (!process->waitForStarted(3000)) {
 		LYXERR0("Qprocess " << cmd << " did not start!");
@@ -92,13 +95,17 @@ int Systemcall::startscript(Starttype how, string const & what)
 		LYXERR0("state " << process->state());
 		LYXERR0("status " << process->exitStatus());
 	}
-	if (!os::terminal_output()) {
-	    // The output may have been redirected. But even if we are not
-	    // running in a terminal, the output could go to some log file,
-	    // for example ~/.xsession-errors on *nix.
-	    cout << fromqstr(QString::fromLocal8Bit(process->readAllStandardOutput().data())) << endl;
-	    cerr << fromqstr(QString::fromLocal8Bit(process->readAllStandardError().data())) << endl;
-	}
+
+	// If the output has been redirected, we write it all at once.
+	// Even if we are not running in a terminal, the output could go
+	// to some log file, for example ~/.xsession-errors on *nix.
+	if (!os::is_terminal(os::STDOUT))
+		cout << fromqstr(QString::fromLocal8Bit(
+			    process->readAllStandardOutput().data()));
+	if (!os::is_terminal(os::STDERR))
+		cerr << fromqstr(QString::fromLocal8Bit(
+			    process->readAllStandardError().data()));
+
 	killProcess(process);
 	return exit_code;
 #endif
diff --git a/src/support/os.h b/src/support/os.h
index b5d1fecd80..1644ef4bf0 100644
--- a/src/support/os.h
+++ b/src/support/os.h
@@ -27,6 +27,12 @@ enum shell_type {
 	CMD_EXE
 };
 
+enum io_channel {
+	STDIN = 0,
+	STDOUT,
+	STDERR
+};
+
 /// Do some work just once.
 void init(int argc, char * argv[]);
 
@@ -39,9 +45,8 @@ std::string const & stdoutdev();
 /// Returns the name of the stderr device (/dev/stderr, /dev/tty, conout$).
 std::string const & stderrdev();
 
-/// Tells whether LyX is being run from a terminal and stdout/stderr are
-/// not redirected.
-bool terminal_output();
+/// Tells whether \p channel is connected to a terminal or not. 
+bool is_terminal(io_channel channel);
 
 /// Returns "/" on *nix, "C:/", etc on Windows.
 std::string current_root();
diff --git a/src/support/os_cygwin.cpp b/src/support/os_cygwin.cpp
index 840a11ccc1..068d7035d6 100644
--- a/src/support/os_cygwin.cpp
+++ b/src/support/os_cygwin.cpp
@@ -254,9 +254,9 @@ string const & stderrdev()
 }
 
 
-bool terminal_output()
+bool is_terminal(io_channel channel)
 {
-	return isatty(1) && isatty(2);
+	return isatty(channel);
 }
 
 
diff --git a/src/support/os_unix.cpp b/src/support/os_unix.cpp
index ccc04b69e2..a9ae59850c 100644
--- a/src/support/os_unix.cpp
+++ b/src/support/os_unix.cpp
@@ -157,9 +157,9 @@ string const & stderrdev()
 }
 
 
-bool terminal_output()
+bool is_terminal(io_channel channel)
 {
-	return isatty(1) && isatty(2);
+	return isatty(channel);
 }
 
 
diff --git a/src/support/os_win32.cpp b/src/support/os_win32.cpp
index f17f06de5f..464d8df111 100644
--- a/src/support/os_win32.cpp
+++ b/src/support/os_win32.cpp
@@ -310,7 +310,7 @@ string const & stderrdev()
 }
 
 
-bool terminal_output()
+bool is_terminal(io_channel channel)
 {
 	// FIXME: Passing conout$ to Qt fails, most probably for the
 	// reason explained here: