diff --git a/riverguile.c b/riverguile.c
index 8b3ccf6..25acf15 100644
--- a/riverguile.c
+++ b/riverguile.c
@@ -52,7 +52,7 @@ static bool scm2uint(uint32_t *x, SCM s)
 {
 	if ( scm_is_false(scm_number_p(s)) == 1 )
 		return false;
-	*x = scm_to_uint32(scm_inexact_to_exact(s));
+	*x = scm_to_uint32(scm_inexact_to_exact(scm_round_number(s)));
 	return true;
 }