diff --git a/test-bn.scm b/test-bn.scm
index a6f6865a..1638c91f 100644
--- a/test-bn.scm
+++ b/test-bn.scm
@@ -2,7 +2,7 @@
 
  (define-c bn-test
    "(void *data, int argc, closure _, object k, object fx)"
-   " object bn = Cyc_int2bignum2(data, fx);
+   " object bn = Cyc_int2bignum2(data, obj_obj2int(fx));
      return_closcall1(data, k, bn); ")
 
  (repl)