diff --git a/CHANGES b/CHANGES
index 8f1384820..b3b34dcb6 100644
--- a/CHANGES
+++ b/CHANGES
@@ -22,6 +22,7 @@ Bugs fixed
 * #10031: py domain: Fix spurious whitespace in unparsing various operators (``+``,
   ``-``, ``~``, and ``**``). Patch by Adam Turner.
 * #10460: logging: Always show node source locations as absolute paths.
+* #10520: HTML Theme: Fix use of sidebar classes in ``agogo.css_t``.
 
 Testing
 --------
diff --git a/sphinx/themes/agogo/static/agogo.css_t b/sphinx/themes/agogo/static/agogo.css_t
index 14c5e52ce..53c4c3848 100644
--- a/sphinx/themes/agogo/static/agogo.css_t
+++ b/sphinx/themes/agogo/static/agogo.css_t
@@ -273,12 +273,6 @@ div.document ol {
 
 div.sidebar,
 aside.sidebar {
-  width: {{ theme_sidebarwidth|todim }};
-  {%- if theme_rightsidebar|tobool %}
-  float: right;
-  {%- else %}
-  float: left;
-  {%- endif %}
   font-size: .9em;
 }