diff --git a/wp-admin/css/wp-admin.css b/wp-admin/css/wp-admin.css
index d0d0714c48..9fd22a5a7d 100644
--- a/wp-admin/css/wp-admin.css
+++ b/wp-admin/css/wp-admin.css
@@ -3500,6 +3500,10 @@ td.plugin-title p {
 /*------------------------------------------------------------------------------
   11.2 - Post Revisions
 ------------------------------------------------------------------------------*/
+body.revision-php {
+	overflow-y: scroll; /* Force a scrollbar, so centering doesn't jump */
+}
+
 .revisions-control-frame,
 .revisions-diff-frame {
 	position: relative;