diff --git a/sources/TerminalStrip/UndoCommand/addterminalstripcommand.cpp b/sources/TerminalStrip/UndoCommand/addterminalstripcommand.cpp
index fc88b41c6..df0ae0875 100644
--- a/sources/TerminalStrip/UndoCommand/addterminalstripcommand.cpp
+++ b/sources/TerminalStrip/UndoCommand/addterminalstripcommand.cpp
@@ -38,13 +38,13 @@ AddTerminalStripCommand::~AddTerminalStripCommand()
 {}
 
 void AddTerminalStripCommand::undo() {
-	if (m_project && m_strip) {
-		m_project->addTerminalStrip(m_strip);
-	}
+        if (m_project && m_strip) {
+                m_project->removeTerminalStrip(m_strip);
+        }
 }
 
 void AddTerminalStripCommand::redo() {
-	if (m_project && m_strip) {
-		m_project->removeTerminalStrip(m_strip);
-	}
+    if (m_project && m_strip) {
+            m_project->addTerminalStrip(m_strip);
+    }
 }
diff --git a/sources/TerminalStrip/UndoCommand/addterminalstripcommand.h b/sources/TerminalStrip/UndoCommand/addterminalstripcommand.h
index 218e45599..495f92c3d 100644
--- a/sources/TerminalStrip/UndoCommand/addterminalstripcommand.h
+++ b/sources/TerminalStrip/UndoCommand/addterminalstripcommand.h
@@ -27,7 +27,7 @@ class QETProject;
 class AddTerminalStripCommand : public QUndoCommand
 {
     public:
-        AddTerminalStripCommand(TerminalStrip *strip, QETProject *project, QUndoCommand *parent);
+		AddTerminalStripCommand(TerminalStrip *strip, QETProject *project, QUndoCommand *parent = nullptr);
         ~AddTerminalStripCommand() override;
 
 		void undo() override;
diff --git a/sources/qetproject.cpp b/sources/qetproject.cpp
index 8b9ab3cb2..a32414e6e 100644
--- a/sources/qetproject.cpp
+++ b/sources/qetproject.cpp
@@ -1857,7 +1857,7 @@ bool QETProject::addTerminalStrip(TerminalStrip *strip)
 	if (strip->parent() != this)
 		return false;
 
-	if (!m_terminal_strip_vector.contains(strip))
+	if (m_terminal_strip_vector.contains(strip))
 		return true;
 
 	m_terminal_strip_vector.append(strip);