diff --git a/theme/boost/scss/moodle/debug.scss b/theme/boost/scss/moodle/debug.scss
index a534c9cbfbc..9f1f0745c74 100644
--- a/theme/boost/scss/moodle/debug.scss
+++ b/theme/boost/scss/moodle/debug.scss
@@ -40,6 +40,13 @@ body.behat-site {
             content: none;
         }
     }
+
+    // Workaround for MDL-70411.
+    // Pad the side of the message drawer out slightly to ensure that Firefox scroll bar does not cover controls at the
+    // edge of the screen.
+    [data-region="message-drawer"] {
+        padding-right: 10px;
+    }
 }
 
 .phpinfo table,
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index e3a76469231..7c7eaf91af5 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -18787,6 +18787,9 @@ body.behat-site .custom-control-input {
 body.behat-site .custom-control-label::before, body.behat-site .custom-control-label::after {
   content: none; }
 
+body.behat-site [data-region="message-drawer"] {
+  padding-right: 10px; }
+
 .phpinfo table,
 .phpinfo th,
 .phpinfo h2 {
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index 21d48152b5f..ae6878beb79 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -18968,6 +18968,9 @@ body.behat-site .custom-control-input {
 body.behat-site .custom-control-label::before, body.behat-site .custom-control-label::after {
   content: none; }
 
+body.behat-site [data-region="message-drawer"] {
+  padding-right: 10px; }
+
 .phpinfo table,
 .phpinfo th,
 .phpinfo h2 {