diff --git a/libguile/vm-i-scheme.c b/libguile/vm-i-scheme.c
index ff963d64c..73c4296a5 100644
--- a/libguile/vm-i-scheme.c
+++ b/libguile/vm-i-scheme.c
@@ -285,6 +285,12 @@ VM_DEFINE_FUNCTION (126, mod, "mod", 2)
 /*
  * GOOPS support
  */
+VM_DEFINE_FUNCTION (169, class_of, "class-of", 1)
+{
+  ARGS1 (obj);
+  RETURN (SCM_INSTANCEP (obj) ? SCM_CLASS_OF (obj) : scm_class_of (obj));
+}
+
 VM_DEFINE_FUNCTION (127, slot_ref, "slot-ref", 2)
 {
   size_t slot;
diff --git a/module/language/tree-il/compile-glil.scm b/module/language/tree-il/compile-glil.scm
index 16212bb55..c708fe65d 100644
--- a/module/language/tree-il/compile-glil.scm
+++ b/module/language/tree-il/compile-glil.scm
@@ -103,6 +103,7 @@
    ((list? . 1) . list?)
    (list . list)
    (vector . vector)
+   ((class-of . 1) . class-of)
    ((@slot-ref . 2) . slot-ref)
    ((@slot-set! . 3) . slot-set)
    ((vector-ref . 2) . vector-ref)
diff --git a/module/oop/goops.scm b/module/oop/goops.scm
index 00a5d68d3..a9e26b5aa 100644
--- a/module/oop/goops.scm
+++ b/module/oop/goops.scm
@@ -82,6 +82,12 @@
 (eval-when (eval load compile)
   (%init-goops-builtins))
 
+(eval-when (eval load compile)
+  (use-modules ((language tree-il primitives) :select (add-interesting-primitive!)))
+  (add-interesting-primitive! 'class-of)
+  (add-interesting-primitive! '@slot-ref)
+  (add-interesting-primitive! '@slot-set!))
+
 ;; Then load the rest of GOOPS
 (use-modules (oop goops util)
 	     (oop goops dispatch)
@@ -1125,11 +1131,6 @@
 ;; the idea is to compile the index into the procedure, for fastest
 ;; lookup. Also, @slot-ref and @slot-set! have their own bytecodes.
 
-(eval-when (compile)
-  (use-modules ((language tree-il primitives) :select (add-interesting-primitive!)))
-  (add-interesting-primitive! '@slot-ref)
-  (add-interesting-primitive! '@slot-set!))
-
 (eval-when (eval load compile)
   (define num-standard-pre-cache 20))