diff --git a/tools/lammps-gui/TODO.md b/tools/lammps-gui/TODO.md
index f6c97c12b6..f9fd7b4dde 100644
--- a/tools/lammps-gui/TODO.md
+++ b/tools/lammps-gui/TODO.md
@@ -2,7 +2,6 @@ LAMMPS-GUI TODO list:
 
 # Short term goals
 
-- add indicator for when the file in editor is modified (-> status bar?)
 - add "Help" entry to menu bar. Should open a popup window with a one page description of how to use it. Use HTML or Markdown text.
 - add dialog when exiting asking if file should be saved when it is modified, similar dialog when opening a new file
 - add CTRL-q hotkey to log windows so you can exit the entire application (add do you really want to? dialog to this)
diff --git a/tools/lammps-gui/lammpsgui.cpp b/tools/lammps-gui/lammpsgui.cpp
index 4f6d7d74fa..f88c892f7e 100644
--- a/tools/lammps-gui/lammpsgui.cpp
+++ b/tools/lammps-gui/lammpsgui.cpp
@@ -70,6 +70,8 @@ LammpsGui::LammpsGui(QWidget *parent, const char *filename) :
     connect(ui->actionStop_LAMMPS, &QAction::triggered, this, &LammpsGui::stop_run);
     connect(ui->actionAbout_LAMMPS_GUI, &QAction::triggered, this, &LammpsGui::about);
     connect(ui->action_Help, &QAction::triggered, this, &LammpsGui::help);
+    connect(ui->textEdit->document(), &QTextDocument::modificationChanged, this,
+            &LammpsGui::modified);
 
 #if !QT_CONFIG(clipboard)
     ui->actionCut->setEnabled(false);
@@ -158,6 +160,7 @@ void LammpsGui::open_file(const QString &fileName)
     QString text = in.readAll();
     ui->textEdit->document()->setPlainText(text);
     ui->textEdit->moveCursor(QTextCursor::Start, QTextCursor::MoveAnchor);
+    ui->textEdit->document()->setModified(false);
     file.close();
 }
 
@@ -175,6 +178,7 @@ void LammpsGui::write_file(const QString &fileName)
     QString text = ui->textEdit->toPlainText();
     out << text;
     file.close();
+    ui->textEdit->document()->setModified(false);
 }
 
 void LammpsGui::save()
@@ -286,6 +290,16 @@ void LammpsGui::logupdate()
     }
 }
 
+void LammpsGui::modified()
+{
+    const QString modflag(" - *modified*");
+    auto title = windowTitle().remove(modflag);
+    if (ui->textEdit->document()->isModified())
+        setWindowTitle(title + modflag);
+    else
+        setWindowTitle(title);
+}
+
 void LammpsGui::run_done()
 {
     logupdater->stop();
diff --git a/tools/lammps-gui/lammpsgui.h b/tools/lammps-gui/lammpsgui.h
index 1ce4946bec..8e729c388a 100644
--- a/tools/lammps-gui/lammpsgui.h
+++ b/tools/lammps-gui/lammpsgui.h
@@ -64,6 +64,7 @@ private slots:
     void about();
     void help();
     void logupdate();
+    void modified();
 
 private:
     Ui::LammpsGui *ui;