diff --git a/theme/bootstrapbase/less/bootstrap/sprites.less b/theme/bootstrapbase/less/bootstrap/sprites.less
index 1812bf71acb..aa1937f05d1 100644
--- a/theme/bootstrapbase/less/bootstrap/sprites.less
+++ b/theme/bootstrapbase/less/bootstrap/sprites.less
@@ -14,8 +14,8 @@
 // For the white version of the icons, just add the .icon-white class:
 // <i class="icon-inbox icon-white"></i>
 
-[class^="icon-"],
-[class*=" icon-"] {
+[class^="icon-"]:not([class^="icon-size-"]),
+[class*=" icon-"]:not([class*=" icon-size-"]) {
   display: inline-block;
   width: 14px;
   height: 14px;
diff --git a/theme/bootstrapbase/readme_moodle.txt b/theme/bootstrapbase/readme_moodle.txt
index 0c28edb9563..238ea14cdc9 100644
--- a/theme/bootstrapbase/readme_moodle.txt
+++ b/theme/bootstrapbase/readme_moodle.txt
@@ -12,6 +12,7 @@ To update to the latest release of twitter bootstrap:
 * download the new less files and store them in less/bootstrap
 * Apply change in MDL-42195 (We don't want responsive images by default).
 * Apply change in MDL-48328 (We need to reset the width of the container directly, in ./less/bootstrap/navbar.less, using the calculated value found in ./less/bootstrap/mixin.less).
+* Apply change in MDL-64091 (We don't want icon-size-n classes to have the icon background image applied).
 * regenerate css files using grunt
 * update ./thirdpartylibs.xml
 
diff --git a/theme/bootstrapbase/style/editor.css b/theme/bootstrapbase/style/editor.css
index 4fbae66b091..83a4ea01970 100644
--- a/theme/bootstrapbase/style/editor.css
+++ b/theme/bootstrapbase/style/editor.css
@@ -774,8 +774,8 @@ table th[class*="span"],
 .table-hover tbody tr.info:hover > td {
   background-color: #c4e3f3;
 }
-[class^="icon-"],
-[class*=" icon-"] {
+[class^="icon-"]:not([class^="icon-size-"]),
+[class*=" icon-"]:not([class*=" icon-size-"]) {
   display: inline-block;
   width: 14px;
   height: 14px;
diff --git a/theme/bootstrapbase/style/moodle.css b/theme/bootstrapbase/style/moodle.css
index c2724a4779e..66449ffb091 100644
--- a/theme/bootstrapbase/style/moodle.css
+++ b/theme/bootstrapbase/style/moodle.css
@@ -12552,8 +12552,8 @@ table th[class*="span"],
 .table-hover tbody tr.info:hover > td {
   background-color: #c4e3f3;
 }
-[class^="icon-"],
-[class*=" icon-"] {
+[class^="icon-"]:not([class^="icon-size-"]),
+[class*=" icon-"]:not([class*=" icon-size-"]) {
   display: inline-block;
   width: 14px;
   height: 14px;