diff --git a/module/language/tree-il/primitives.scm b/module/language/tree-il/primitives.scm
index 531a14a4b..50a002da6 100644
--- a/module/language/tree-il/primitives.scm
+++ b/module/language/tree-il/primitives.scm
@@ -79,7 +79,8 @@
 
 (define (add-interesting-primitive! name)
   (hashq-set! *interesting-primitive-vars*
-              (module-variable (current-module) name)
+              (or (module-variable (current-module) name)
+                  (error "unbound interesting primitive" name))
               name))
 
 (define *interesting-primitive-vars* (make-hash-table))
diff --git a/module/oop/goops.scm b/module/oop/goops.scm
index 2e96e0b03..bf13e3830 100644
--- a/module/oop/goops.scm
+++ b/module/oop/goops.scm
@@ -84,6 +84,10 @@
 (eval-when (eval load compile)
   (use-modules ((language tree-il primitives) :select (add-interesting-primitive!)))
   (add-interesting-primitive! 'class-of)
+  (define (@slot-ref o n)
+    (struct-ref o n))
+  (define (@slot-set! o n v)
+    (struct-set! o n v))
   (add-interesting-primitive! '@slot-ref)
   (add-interesting-primitive! '@slot-set!))