diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index f4a0b82753..a593c54b15 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -10093,7 +10093,18 @@ SetStyleShapeSourceToCSSValue(
   if (basicShape) {
     aShapeSource->SetBasicShape(basicShape, referenceBox);
   } else {
-    aShapeSource->SetReferenceBox(referenceBox);
+    if (mozilla::IsSame<ReferenceBox, StyleGeometryBox>::value && 
+      referenceBox != ReferenceBox::NoBox) {
+      RefPtr<StyleBasicShape> defaultInset = new StyleBasicShape(StyleBasicShapeType::Inset);
+      nsStyleCoord zero;
+      zero.SetCoordValue(0);
+      for (int i = 0; i < 4; i++) {
+        defaultInset->Coordinates().AppendElement(zero);
+      }
+      aShapeSource->SetBasicShape(defaultInset, referenceBox);
+    } else {
+      aShapeSource->SetReferenceBox(referenceBox);
+    }
   }
 }