diff --git a/extensions/lang-english/locale/core.yml b/extensions/lang-english/locale/core.yml
index 174b0f0e5..d7fc4e588 100644
--- a/extensions/lang-english/locale/core.yml
+++ b/extensions/lang-english/locale/core.yml
@@ -46,7 +46,7 @@ core:
 
     # These translations are used in the Edit Custom CSS modal dialog.
     edit_css:
-      customize_text: Customize your forum's appearance by adding your own LESS/CSS code to be applied on top of Flarum's <a>default styles</a>.
+      customize_text: "Customize your forum's appearance by adding your own LESS/CSS code to be applied on top of Flarum's <a>default styles</a>."
       submit_button: => core.ref.save_changes
       title: