diff --git a/phpBB/styles/prosilver/theme/stylesheet.css b/phpBB/styles/prosilver/theme/stylesheet.css
index bdd35fd409..0c29ccee30 100644
--- a/phpBB/styles/prosilver/theme/stylesheet.css
+++ b/phpBB/styles/prosilver/theme/stylesheet.css
@@ -7,15 +7,15 @@
     --------------------------------------------------------------
 */
 
-@import url('normalize.css');
-@import url('base.css');
-@import url('utilities.css');
-@import url('common.css');
-@import url('links.css');
-@import url('content.css');
-@import url('buttons.css');
-@import url('cp.css');
-@import url('forms.css');
-@import url('icons.css');
-@import url('colours.css');
-@import url('responsive.css');
+@import url('normalize.css?v=3.3');
+@import url('base.css?v=3.3');
+@import url('utilities.css?v=3.3');
+@import url('common.css?v=3.3');
+@import url('links.css?v=3.3');
+@import url('content.css?v=3.3');
+@import url('buttons.css?v=3.3');
+@import url('cp.css?v=3.3');
+@import url('forms.css?v=3.3');
+@import url('icons.css?v=3.3');
+@import url('colours.css?v=3.3');
+@import url('responsive.css?v=3.3');