diff --git a/CHANGELOG.md b/CHANGELOG.md
index 57202cd..ae5745c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
  * Make it easier to check on or off the checkbox by adding some buffer (instead of having to precisely click inside it)
  * Prevent double-click of checkbox leading to selecting/highlighting it
  * Slightly fade the text of a checkbox line if the checkbox is checked.
+ * Fix weekend date colours being incorrect on theme change while app is running
 
 # 0.5.2
 
diff --git a/bouquin/main_window.py b/bouquin/main_window.py
index 0e5e454..710fca7 100644
--- a/bouquin/main_window.py
+++ b/bouquin/main_window.py
@@ -1026,10 +1026,12 @@ class MainWindow(QMainWindow):
         self.editor.viewport().update()
 
     def _apply_calendar_text_colors(self):
-        pal = self.palette()
+        pal = QApplication.instance().palette()
         txt = pal.windowText().color()
+
         fmt = QTextCharFormat()
         fmt.setForeground(txt)
+
         # Use normal text color for weekends
         self.calendar.setWeekdayTextFormat(Qt.Saturday, fmt)
         self.calendar.setWeekdayTextFormat(Qt.Sunday, fmt)