diff --git a/theme/bootstrapbase/less/moodle/forms.less b/theme/bootstrapbase/less/moodle/forms.less
index dcaad6d6a5c..940a181b82d 100644
--- a/theme/bootstrapbase/less/moodle/forms.less
+++ b/theme/bootstrapbase/less/moodle/forms.less
@@ -122,6 +122,15 @@ form {
     margin-right: .3em;
 }
 
+.custom-select {
+    max-width: 100%;
+}
+
+// Make the submit button align with the .custom-select element.
+.custom-select + input[type="submit"] {
+    margin: 0 0 0 5px;
+}
+
 #portfolio-add-button {
     display: inline;
 }
diff --git a/theme/bootstrapbase/style/moodle.css b/theme/bootstrapbase/style/moodle.css
index 65c23c7c6f6..fd5b4a49a38 100644
--- a/theme/bootstrapbase/style/moodle.css
+++ b/theme/bootstrapbase/style/moodle.css
@@ -16559,6 +16559,12 @@ form {
 .singleselect label {
   margin-right: .3em;
 }
+.custom-select {
+  max-width: 100%;
+}
+.custom-select + input[type="submit"] {
+  margin: 0 0 0 5px;
+}
 #portfolio-add-button {
   display: inline;
 }