diff --git a/runtime/Unsafe/bignumber.scm b/runtime/Unsafe/bignumber.scm
index 8411ee842..e4498637b 100644
--- a/runtime/Unsafe/bignumber.scm
+++ b/runtime/Unsafe/bignumber.scm
@@ -132,7 +132,7 @@
 	    "GCD_BIGNUM")
 	 (method static $lcmbx::bignum (::bignum ::bignum)
 	    "LCM_BIGNUM")
-	 (method static $bignum->string::string (::bignum ::long)
+	 (method static $bignum->string::string (::bignum ::int)
 	    "bgl_bignum_to_string")
 	 (method static $string->bignum::bignum (::string ::int)
 	    "bgl_string_to_bignum")