source elements within a picture element can contain width/height. See: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/source#sizes.

Author: johns996

sass/themes/_error.scss

@@ -877,17 +877,17 @@ Therefore it shouldn't be used in markup, except for `<img>`. Use CSS instead.
 
 ### Selector
 ```css
-:not(img, object, embed, svg, canvas)[width],
-:not(img, object, embed, svg, canvas)[height]
+:not(img, object, embed, svg, canvas, picture > source)[width],
+:not(img, object, embed, svg, canvas, picture > source)[height]
 ```
 
 ### Test
 ``` html
 <p width="20">Damned! I feel sooo strait :(</p>
 ```
 */
-:not(img, object, embed, svg, canvas)[width],
-:not(img, object, embed, svg, canvas)[height] {
+:not(img, object, embed, svg, canvas, picture > source)[width],
+:not(img, object, embed, svg, canvas, picture > source)[height] {
   @include error('dimensions');
 
   @include void-tags {