diff --git a/theme/base/style/dock.css b/theme/base/style/dock.css
index dc1b8c348da..e61ed5b56dc 100644
--- a/theme/base/style/dock.css
+++ b/theme/base/style/dock.css
@@ -7,7 +7,7 @@
 body.has_dock {margin-left:30px;}
 
 /** For the dock itself */
-#dock {width:30px;position:fixed;top:0px;left:0px;height:100%;background-color:#FFF;border-right:1px solid #000;z-index:11000;}
+#dock {width:30px;position:fixed;top:0px;left:0px;height:100%;background-color:#FFF;border-right:1px solid #000;z-index:5000;}
 #dock.nothingdocked {visibility: hidden;display:none;}
 #dock .dockeditem .firstdockitem {margin-top:1em;}
 #dock .dockedtitle {border-bottom:1px solid #000;border-top:1px solid #000;cursor:pointer;}
diff --git a/theme/upgrade.txt b/theme/upgrade.txt
index 6cbd99ef182..01d33174e62 100644
--- a/theme/upgrade.txt
+++ b/theme/upgrade.txt
@@ -22,6 +22,9 @@ Removed themes:
   If you wish to keep your theme and its settings, download it from moodle.org and put it back in
   the theme/ directory BEFORE UPGRADING.
 
+Notes:
+* z-index on #dock has been adjusted from 11000 to 5000 to prevent overlapping issues with fullscreen TinyMCE in Base theme.
+
 === 2.6 ===
 
 Removed themes: