diff --git a/components/layout_2020/dom_traversal.rs b/components/layout_2020/dom_traversal.rs
index a8f5a17fc1d..c043d3b75d3 100644
--- a/components/layout_2020/dom_traversal.rs
+++ b/components/layout_2020/dom_traversal.rs
@@ -346,8 +346,10 @@ impl BoxSlot<'_> {
 
 impl Drop for BoxSlot<'_> {
     fn drop(&mut self) {
-        if let Some(slot) = &mut self.slot {
-            assert!(slot.borrow().is_some(), "failed to set a layout box");
+        if !std::thread::panicking() {
+            if let Some(slot) = &mut self.slot {
+                assert!(slot.borrow().is_some(), "failed to set a layout box");
+            }
         }
     }
 }