diff --git a/src/calibre/gui2/__init__.py b/src/calibre/gui2/__init__.py
index 0fd4054763..586424dc4c 100644
--- a/src/calibre/gui2/__init__.py
+++ b/src/calibre/gui2/__init__.py
@@ -538,7 +538,7 @@ class Application(QApplication):
 
 def is_ok_to_use_qt():
     global gui_thread
-    if islinux and os.environ.get('DISPLAY', None) is None:
+    if islinux and ':' in os.environ.get('DISPLAY', ''):
         return False
     if QApplication.instance() is None:
         QApplication([])