diff --git a/src/vm.c b/src/vm.c
index ae8494ee..bc3c78bc 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -278,10 +278,14 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
     CASE(OP_LAMBDA) {
       struct pic_proc *proc;
       struct pic_env *env;
+      int i;
 
       env = (struct pic_env *)pic_obj_alloc(pic, sizeof(struct pic_env), PIC_TT_ENV);
       env->num_val = pic->irep[pc->u.i]->argc;
       env->values = (pic_value *)pic_alloc(pic, sizeof(pic_value) * env->num_val);
+      for (i = 0; i < env->num_val; ++i) {
+	env->values[i] = pic_undef_value();
+      }
       env->up = pic_proc_ptr(*pic->ci->fp)->env;
 
       proc = pic_proc_new(pic, pic->irep[pc->u.i], env);