--- a/src/code/condition.lisp
+++ b/src/code/condition.lisp
@@ -315,7 +315,8 @@
 				      "new"
 				      (layout-length layout)
 				      (layout-inherits layout)
-				      (layout-depthoid layout))
+				      (layout-depthoid layout)
+				      (layout-n-untagged-slots layout))
 	     (register-layout layout :invalidate t))
 	    ((not (classoid-layout class))
 	     (register-layout layout)))