diff --git a/src/math/big/ratconv.go b/src/math/big/ratconv.go
index 90053a9c81d..dadd4d7b8ee 100644
--- a/src/math/big/ratconv.go
+++ b/src/math/big/ratconv.go
@@ -113,7 +113,7 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
 
 	// special-case 0 (see also issue #16176)
 	if len(z.a.abs) == 0 {
-		return z, true
+		return z.norm(), true
 	}
 	// len(z.a.abs) > 0
 
diff --git a/src/math/big/ratconv_test.go b/src/math/big/ratconv_test.go
index e55e6557189..45a35608f4b 100644
--- a/src/math/big/ratconv_test.go
+++ b/src/math/big/ratconv_test.go
@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"math"
+	"reflect"
 	"strconv"
 	"strings"
 	"testing"
@@ -205,6 +206,14 @@ func TestRatSetString(t *testing.T) {
 	}
 }
 
+func TestRatSetStringZero(t *testing.T) {
+	got, _ := new(Rat).SetString("0")
+	want := new(Rat).SetInt64(0)
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("got %#+v, want %#+v", got, want)
+	}
+}
+
 func TestRatScan(t *testing.T) {
 	var buf bytes.Buffer
 	for i, test := range setStringTests {