diff --git a/scss/_functions.scss b/scss/_functions.scss
index eb2471d75368..9c06603150ed 100644
--- a/scss/_functions.scss
+++ b/scss/_functions.scss
@@ -51,6 +51,9 @@
 }
 
 // See https://codepen.io/kevinweber/pen/dXWoRw
+//
+// Requires the use of quotes around data URIs.
+
 @function escape-svg($string) {
   @if str-index($string, "data:image/svg+xml") {
     @each $char, $encoded in $escaped-characters {