--- a/devtools/client/inspector/boxmodel/test/browser_boxmodel_pseudo-element.js
+++ b/devtools/client/inspector/boxmodel/test/browser_boxmodel_pseudo-element.js
@@ -48,25 +48,25 @@ const res1 = [
     value: "32"
   },
   {
     selector: ".boxmodel-margin.boxmodel-top > span",
     value: 0
   },
   {
     selector: ".boxmodel-margin.boxmodel-left > span",
-    value: 0
+    value: 4 // (100 - (10 * 2) - (20 * 2) - 32) / 2
   },
   {
     selector: ".boxmodel-margin.boxmodel-bottom > span",
     value: 6
   },
   {
     selector: ".boxmodel-margin.boxmodel-right > span",
-    value: 0
+    value: 4 // (100 - (10 * 2) - (20 * 2) - 32) / 2
   },
   {
     selector: ".boxmodel-padding.boxmodel-top > span",
     value: 0
   },
   {
     selector: ".boxmodel-padding.boxmodel-left > span",
     value: 0