diff --git a/python/utils.py b/python/utils.py
index 241af1ed48e..04bcd0e9331 100644
--- a/python/utils.py
+++ b/python/utils.py
@@ -30,7 +30,7 @@ QGIS utilities module
 
 from qgis.PyQt.QtCore import QCoreApplication, QLocale, QThread
 from qgis.PyQt.QtWidgets import QPushButton, QApplication
-from qgis.core import Qgis, QgsExpression, QgsMessageLog, qgsfunction, QgsMessageOutput, QgsWkbTypes, QgsApplication
+from qgis.core import Qgis, QgsExpression, QgsMessageLog, qgsfunction, QgsMessageOutput, QgsWkbTypes
 from qgis.gui import QgsMessageBar
 
 import sys
@@ -133,7 +133,7 @@ def show_message_log(pop_error=True):
 
 
 def open_stack_dialog(type, value, tb, msg, pop_error=True):
-    if pop_error:
+    if pop_error and iface is not None:
         iface.messageBar().popWidget()
 
     if msg is None:
@@ -189,7 +189,7 @@ def open_stack_dialog(type, value, tb, msg, pop_error=True):
 
 def qgis_excepthook(type, value, tb):
     # detect if running in the main thread
-    in_main_thread = QThread.currentThread() == QgsApplication.instance().thread()
+    in_main_thread = QCoreApplication.instance() is None or QThread.currentThread() == QCoreApplication.instance().thread()
 
     # only use messagebar if running in main thread - otherwise it will crash!
     showException(type, value, tb, None, messagebar=in_main_thread)