diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 045d672e..c2e0317a 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -178,6 +178,7 @@ object Cyc_num_fast_lte_op(void *data, object x, object y);
 object Cyc_num_cmp_va_list(void *data, int argc,
                            int (fn_op(void *, object, object)), object n,
                            va_list ns);
+void Cyc_expt(void *data, object cont, object x, object y);
 object Cyc_eq(object x, object y);
 object Cyc_set_cell(void *, object l, object val);
 object Cyc_set_car(void *, object l, object val);
diff --git a/scheme/base.sld b/scheme/base.sld
index df8128a8..136c493f 100644
--- a/scheme/base.sld
+++ b/scheme/base.sld
@@ -1163,11 +1163,7 @@
   (define (square z) (* z z))
   (define-c expt
     "(void *data, int argc, closure _, object k, object z1, object z2)"
-    " make_double(d, 0.0);
-      Cyc_check_num(data, z1);
-      Cyc_check_num(data, z2);
-      d.value = pow( unbox_number(z1), unbox_number(z2) );
-      return_closcall1(data, k, &d); ")
+    " Cyc_expt(data, k, z1, z2); ")
   (define-c eof-object
     "(void *data, int argc, closure _, object k)"
     " return_closcall1(data, k, Cyc_EOF); ")