diff --git a/django/contrib/admin/static/admin/css/changelists.css b/django/contrib/admin/static/admin/css/changelists.css
index 7b8b9c7719..a164254031 100644
--- a/django/contrib/admin/static/admin/css/changelists.css
+++ b/django/contrib/admin/static/admin/css/changelists.css
@@ -128,6 +128,7 @@
 /* FILTER COLUMN */
 
 #changelist-filter {
+    flex: 0 0 240px;
     order: 1;
     width: 240px;
     background: #f8f8f8;
diff --git a/django/contrib/admin/static/admin/css/responsive.css b/django/contrib/admin/static/admin/css/responsive.css
index ef968c239e..053e84132f 100644
--- a/django/contrib/admin/static/admin/css/responsive.css
+++ b/django/contrib/admin/static/admin/css/responsive.css
@@ -157,7 +157,7 @@ input[type="submit"], button {
     }
 
     #changelist-filter {
-        width: 200px;
+        flex-basis: 200px;
     }
 
     .change-list .filtered .results,
diff --git a/docs/releases/3.1.6.txt b/docs/releases/3.1.6.txt
index dfc60acc95..2d0a48616d 100644
--- a/docs/releases/3.1.6.txt
+++ b/docs/releases/3.1.6.txt
@@ -9,4 +9,5 @@ Django 3.1.6 fixes several bugs in 3.1.5.
 Bugfixes
 ========
 
-* ...
+* Fixed an admin layout issue in Django 3.1 where changelist filter controls 
+  would become squashed (:ticket:`32391`).