diff --git a/bignum.c b/bignum.c
index 37b2de8e..526fa536 100644
--- a/bignum.c
+++ b/bignum.c
@@ -862,7 +862,7 @@ sexp sexp_ratio_round (sexp ctx, sexp a) {
     r = sexp_mul(ctx, r, SEXP_TWO);
     if (sexp_exact_negativep(r)) {sexp_negate(r);}
     if (sexp_unbox_fixnum(sexp_compare(ctx, r, sexp_ratio_denominator(a))) > 0)
-      q = sexp_add(ctx, q, (sexp_exact_positivep(q) ? SEXP_ONE : SEXP_NEG_ONE));
+      q = sexp_add(ctx, q, (sexp_exact_negativep(sexp_ratio_numerator(a)) ? SEXP_NEG_ONE : SEXP_ONE));
   }
   sexp_gc_release2(ctx);
   return q;
diff --git a/tests/r7rs-tests.scm b/tests/r7rs-tests.scm
index 174d9ba8..998abcc4 100644
--- a/tests/r7rs-tests.scm
+++ b/tests/r7rs-tests.scm
@@ -932,6 +932,10 @@
 
 (test 4 (round 7/2))
 (test 7 (round 7))
+(test 1 (round 7/10))
+(test -4 (round -7/2))
+(test -7 (round -7))
+(test -1 (round -7/10))
 
 (test 1/3 (rationalize (exact .3) 1/10))
 (test #i1/3 (rationalize .3 1/10))