diff --git a/src/windows/main_window.py b/src/windows/main_window.py
index bf4bd2d9da..a3aa1d4820 100644
--- a/src/windows/main_window.py
+++ b/src/windows/main_window.py
@@ -2795,7 +2795,7 @@ def setup_toolbars(self):
         self.caption_model_row = None
 
         # Get project's initial zoom value
-        initial_scale = get_app().project.get("scale") or 15.0
+        initial_scale = float(get_app().project.get("scale") or 15.0)
 
         # Setup Zoom Slider widget
         from windows.views.zoom_slider import ZoomSlider
diff --git a/src/windows/views/webview.py b/src/windows/views/webview.py
index 4b7bb4296c..cd1d7d47ff 100644
--- a/src/windows/views/webview.py
+++ b/src/windows/views/webview.py
@@ -230,7 +230,7 @@ def changed(self, action):
         # Reset the scale when loading new JSON
         if action.type == "load":
             # Set the scale again (to project setting)
-            initial_scale = get_app().project.get("scale") or 15.0
+            initial_scale = float(get_app().project.get("scale") or 15.0)
             self.window.sliderZoomWidget.setZoomFactor(initial_scale)
 
     @pyqtSlot(str, bool, bool, bool)
@@ -2829,7 +2829,7 @@ def update_zoom(self, newScale):
         self.redraw_audio_timer.start()
 
         # Only update scale if different
-        current_scale = float(get_app().project.get("scale"))
+        current_scale = float(get_app().project.get("scale") or 15.0)
 
         # Save current zoom
         if newScale != current_scale: