diff --git a/src/backends/octave/octavehighlighter.cpp b/src/backends/octave/octavehighlighter.cpp
index dcdff037..f23aeb0f 100644
--- a/src/backends/octave/octavehighlighter.cpp
+++ b/src/backends/octave/octavehighlighter.cpp
@@ -1,95 +1,95 @@
 /*
     Copyright (C) 2010 Miha Čančula <miha.cancula@gmail.com>
 
     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.
 
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
 
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA  02110-1301, USA.
 */
 
 #include "octavehighlighter.h"
 #include "octavekeywords.h"
 #include "result.h"
 
 #include <QDebug>
 #include <QStringList>
 
 using namespace Cantor;
 
 OctaveHighlighter::OctaveHighlighter(QObject* parent, Session* session): DefaultHighlighter(parent), m_session(session)
 {
   addKeywords(OctaveKeywords::instance()->keywords());
   addFunctions(OctaveKeywords::instance()->functions());
 
   QStringList operators;
   operators
     << QLatin1String("+") << QLatin1String("-") << QLatin1String("*") << QLatin1String("/")
     << QLatin1String(".+") << QLatin1String(".-") << QLatin1String(".*") << QLatin1String("./")
     << QLatin1String("=") << QLatin1String("or") << QLatin1String("and") << QLatin1String("xor")
     << QLatin1String("not") << QLatin1String("||") << QLatin1String("&&") << QLatin1String("==");
   addRules(operators, operatorFormat());
 
   addRule(QRegExp(QLatin1String("\"[^\"]*\"")), stringFormat());
   addRule(QRegExp(QLatin1String("'[^']*'")), stringFormat());
 
   addRule(QRegExp(QLatin1String("#[^\n]*")), commentFormat());
   addRule(QRegExp(QLatin1String("%[^\n]*")), commentFormat());
 
   rehighlight();
 }
 
 void OctaveHighlighter::updateVariables()
 {
   Expression* expr = m_session->evaluateExpression(QLatin1String("who"), Expression::FinishingBehavior::DoNotDelete, true);
   connect(expr, &Expression::statusChanged, [this, expr](Expression::Status status)
   {
     if (status != Expression::Done && status != Expression::Error)
       return;
 
-    if (status == Expression::Done)
+    if (status == Expression::Done && expr->result())
     {
       QString res = expr->result()->toHtml();
       res.replace(QLatin1String("<br/>"),QLatin1String(" "));
       res.remove(0, res.indexOf(QLatin1Char('\n')));
       res.remove(QLatin1Char('\n'));
       res = res.trimmed();
 
       QStringList newVariables;
       foreach ( const QString& var, res.split(QLatin1Char(' '), QString::SkipEmptyParts))
       {
           newVariables <<  var.trimmed();
       }
       qDebug() << "Received" << newVariables.size() << "variables";
 
       for (const QString& newVariable: newVariables)
         if (!m_variables.contains(newVariable))
           addRule(newVariable, variableFormat());
 
       for (const QString& variable: m_variables)
         if (!newVariables.contains(variable))
           removeRule(variable);
 
       m_variables = std::move(newVariables);
       rehighlight();
     }
     expr->deleteLater();
   });
 }
 
 void OctaveHighlighter::sessionStatusChanged(Cantor::Session::Status status)
 {
     if (status == Cantor::Session::Status::Disable)
         for (const QString& variable: m_variables)
             removeRule(variable);
     rehighlight();
 }