diff --git a/django/contrib/admin/static/admin/css/base.css b/django/contrib/admin/static/admin/css/base.css
index 34c0b90e401..fd011a3f9a3 100644
--- a/django/contrib/admin/static/admin/css/base.css
+++ b/django/contrib/admin/static/admin/css/base.css
@@ -441,6 +441,8 @@ select {
 }
 
 select[multiple] {
+    /* Allow HTML size attribute to override the height in the rule above. */
+    height: auto;
     min-height: 150px;
 }