diff --git a/theme/mymobile/config.php b/theme/mymobile/config.php
index 84bfefb7b26..5a2fdd8647c 100644
--- a/theme/mymobile/config.php
+++ b/theme/mymobile/config.php
@@ -156,4 +156,7 @@ if ($thisdevice == "default" || $thisdevice == "tablet" || optional_param('mymob
 
 // Sets a custom render factory to use with the theme, used when working with custom renderers.
 $THEME->rendererfactory = 'theme_overridden_renderer_factory';
-$THEME->csspostprocess = 'mymobile_user_settings';
\ No newline at end of file
+$THEME->csspostprocess = 'mymobile_user_settings';
+
+// Disables CSS Optimiser for MyMobile theme.
+$THEME->supportscssoptimisation = false;