diff --git a/center-content.el b/center-content.el
index 63f3a1a..bedf25c 100644
--- a/center-content.el
+++ b/center-content.el
@@ -23,7 +23,7 @@
 
 (defun center-content--content-pixel-size ()
   "Return the size of the content of the visible text in pixels."
-  (window-text-pixel-size (selected-window) (window-start) (window-end)))
+  (window-text-pixel-size (selected-window) (window-start) (window-end nil t)))
 
 (defun center-content--calculate-left-margin (content-width)
   "Calculate the left margin relative to CONTENT-WIDTH."