diff --git a/mod/forum/report/summary/templates/filters.mustache b/mod/forum/report/summary/templates/filters.mustache
index bc84d0dea49..92c0dc6b8ac 100644
--- a/mod/forum/report/summary/templates/filters.mustache
+++ b/mod/forum/report/summary/templates/filters.mustache
@@ -51,8 +51,8 @@
 
             {{! Start groups filter popover}}
             <div id="filter-groups-popover" class="popover m-t-1 hidden">
-                <h3 class="filter-header">{{# str}} filter:groupsname, forumreport_summary {{/ str}}</h3>
-                <div class="filter-body">
+                <h3 class="popover-header">{{# str}} filter:groupsname, forumreport_summary {{/ str}}</h3>
+                <div class="popover-body">
                     <div class="form-check filter-scrollable">
                         {{#filtergroups}}
                         <input id="filtergroups{{groupid}}" class="form-check-input" type="checkbox" name="filtergroups[]"
diff --git a/theme/boost/scss/moodle.scss b/theme/boost/scss/moodle.scss
index 049ab7c82bc..1b9da99d353 100644
--- a/theme/boost/scss/moodle.scss
+++ b/theme/boost/scss/moodle.scss
@@ -18,7 +18,6 @@ $breadcrumb-divider-rtl: "◀" !default;
 @import "moodle/drawer";
 @import "moodle/dashboard";
 @import "moodle/filemanager";
-@import "moodle/filter";
 @import "moodle/message";
 @import "moodle/question";
 @import "moodle/user";
diff --git a/theme/boost/scss/moodle/filter.scss b/theme/boost/scss/moodle/filter.scss
deleted file mode 100644
index aa10c7e4bd3..00000000000
--- a/theme/boost/scss/moodle/filter.scss
+++ /dev/null
@@ -1,19 +0,0 @@
-/* The button used to display a filter. */
-.filter-button {
-    border-radius: 0.25em;
-    padding: 0.2em;
-}
-
-.filter-header {
-    @extend .popover-header;
-}
-
-.filter-body {
-    @extend .popover-body;
-}
-
-.filter-scrollable {
-    overflow-y: scroll;
-    max-height: 25em;
-    margin-bottom: 1em;
-}
diff --git a/theme/boost/scss/moodle/modules.scss b/theme/boost/scss/moodle/modules.scss
index 5c90985df11..852b709afad 100644
--- a/theme/boost/scss/moodle/modules.scss
+++ b/theme/boost/scss/moodle/modules.scss
@@ -383,6 +383,13 @@ $author-image-margin-sm: 8px;
     }
 }
 
+// Make filter popover content scrollable if needed.
+.filter-scrollable {
+    overflow-y: auto;
+    max-height: 25em;
+    margin-bottom: 1em;
+}
+
 // End styling for mod_forum.
 
 .maincalendar .calendarmonth td,
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index 934871eaa2d..9af3c19b9df 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -6684,7 +6684,7 @@ a.close.disabled, .moodle-dialogue-base a.disabled.closebutton {
       top: 1px;
       border-width: 0 0.5rem 0.5rem 0.5rem;
       border-bottom-color: #fff; }
-  .bs-popover-bottom .popover-header::before, .bs-popover-auto[x-placement^="bottom"] .popover-header::before, .bs-popover-bottom .filter-header::before, .bs-popover-auto[x-placement^="bottom"] .filter-header::before {
+  .bs-popover-bottom .popover-header::before, .bs-popover-auto[x-placement^="bottom"] .popover-header::before {
     position: absolute;
     top: 0;
     left: 50%;
@@ -6710,16 +6710,16 @@ a.close.disabled, .moodle-dialogue-base a.disabled.closebutton {
       border-width: 0.5rem 0 0.5rem 0.5rem;
       border-left-color: #fff; }
 
-.popover-header, .filter-header {
+.popover-header {
   padding: 0.5rem 0.75rem;
   margin-bottom: 0;
   font-size: 0.9375rem;
   background-color: #f7f7f7;
   border-bottom: 1px solid #ebebeb; }
-  .popover-header:empty, .filter-header:empty {
+  .popover-header:empty {
     display: none; }
 
-.popover-body, .filter-body {
+.popover-body {
   padding: 0.5rem 0.75rem;
   color: #373a3c; }
 
@@ -14413,16 +14413,6 @@ a.ygtvspacer:hover {
   display: inline-block;
   padding-left: 5px; }
 
-/* The button used to display a filter. */
-.filter-button {
-  border-radius: 0.25em;
-  padding: 0.2em; }
-
-.filter-scrollable {
-  overflow-y: scroll;
-  max-height: 25em;
-  margin-bottom: 1em; }
-
 /** The message area **/
 .hidden {
   display: none; }
@@ -16303,6 +16293,11 @@ select {
     width: 30px;
     height: 30px; } }
 
+.filter-scrollable {
+  overflow-y: auto;
+  max-height: 25em;
+  margin-bottom: 1em; }
+
 .maincalendar .calendarmonth td,
 .maincalendar .calendarmonth th {
   border: 1px dotted #dee2e6; }
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index d94638703bc..32b53f59b25 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -6930,7 +6930,7 @@ a.close.disabled, .moodle-dialogue-base a.disabled.closebutton {
       top: 1px;
       border-width: 0 0.5rem 0.5rem 0.5rem;
       border-bottom-color: #fff; }
-  .bs-popover-bottom .popover-header::before, .bs-popover-auto[x-placement^="bottom"] .popover-header::before, .bs-popover-bottom .filter-header::before, .bs-popover-auto[x-placement^="bottom"] .filter-header::before {
+  .bs-popover-bottom .popover-header::before, .bs-popover-auto[x-placement^="bottom"] .popover-header::before {
     position: absolute;
     top: 0;
     left: 50%;
@@ -6956,7 +6956,7 @@ a.close.disabled, .moodle-dialogue-base a.disabled.closebutton {
       border-width: 0.5rem 0 0.5rem 0.5rem;
       border-left-color: #fff; }
 
-.popover-header, .filter-header {
+.popover-header {
   padding: 0.5rem 0.75rem;
   margin-bottom: 0;
   font-size: 0.9375rem;
@@ -6964,10 +6964,10 @@ a.close.disabled, .moodle-dialogue-base a.disabled.closebutton {
   border-bottom: 1px solid #ebebeb;
   border-top-left-radius: calc(0.3rem - 1px);
   border-top-right-radius: calc(0.3rem - 1px); }
-  .popover-header:empty, .filter-header:empty {
+  .popover-header:empty {
     display: none; }
 
-.popover-body, .filter-body {
+.popover-body {
   padding: 0.5rem 0.75rem;
   color: #373a3c; }
 
@@ -14675,16 +14675,6 @@ a.ygtvspacer:hover {
   display: inline-block;
   padding-left: 5px; }
 
-/* The button used to display a filter. */
-.filter-button {
-  border-radius: 0.25em;
-  padding: 0.2em; }
-
-.filter-scrollable {
-  overflow-y: scroll;
-  max-height: 25em;
-  margin-bottom: 1em; }
-
 /** The message area **/
 .hidden {
   display: none; }
@@ -16575,6 +16565,11 @@ select {
     width: 30px;
     height: 30px; } }
 
+.filter-scrollable {
+  overflow-y: auto;
+  max-height: 25em;
+  margin-bottom: 1em; }
+
 .maincalendar .calendarmonth td,
 .maincalendar .calendarmonth th {
   border: 1px dotted #dee2e6; }