diff --git a/cura/MachineManagerModel.py b/cura/MachineManagerModel.py
index 43b4ab521d..76786efe61 100644
--- a/cura/MachineManagerModel.py
+++ b/cura/MachineManagerModel.py
@@ -213,7 +213,7 @@ class MachineManagerModel(QObject):
     #   Calling _checkStackForErrors on every change is simply too expensive
     @pyqtProperty(bool, notify = globalValidationChanged)
     def isGlobalStackValid(self):
-        return self._global_stack_valid
+        return bool(self._global_stack_valid)
 
     @pyqtProperty(str, notify = activeStackChanged)
     def activeUserProfileId(self):
diff --git a/resources/qml/MonitorButton.qml b/resources/qml/MonitorButton.qml
index 10fc44b3f0..b8bfbab869 100644
--- a/resources/qml/MonitorButton.qml
+++ b/resources/qml/MonitorButton.qml
@@ -109,7 +109,7 @@ Rectangle
         id: abortButton
 
         visible: printerConnected
-        enabled: Cura.MachineManager.printerOutputDevices[0].jobState == "paused" || Cura.MachineManager.printerOutputDevices[0].jobState == "printing"
+        enabled: printerConnected && Cura.MachineManager.printerOutputDevices[0].jobState == "paused" || Cura.MachineManager.printerOutputDevices[0].jobState == "printing"
 
         height: UM.Theme.getSize("save_button_save_to_button").height
         anchors.top: progressBar.bottom
@@ -156,7 +156,7 @@ Rectangle
         id: pauseButton
 
         visible: printerConnected
-        enabled: Cura.MachineManager.printerOutputDevices[0].jobState == "paused" || Cura.MachineManager.printerOutputDevices[0].jobState == "printing"
+        enabled: printerConnected && Cura.MachineManager.printerOutputDevices[0].jobState == "paused" || Cura.MachineManager.printerOutputDevices[0].jobState == "printing"
 
         height: UM.Theme.getSize("save_button_save_to_button").height
         anchors.top: progressBar.bottom