diff --git a/setup.go b/setup.go
index e011661..eb40307 100644
--- a/setup.go
+++ b/setup.go
@@ -60,7 +60,8 @@ func dns64Parse(c *caddy.Controller) (proxy.Proxy, *net.IPNet, error) {
 				if !c.NextArg() {
 					return prxy, pref, c.ArgErr()
 				}
-				_, pref, err := net.ParseCIDR(c.Val())
+				var err error
+				_, pref, err = net.ParseCIDR(c.Val())
 
 				// test for valid prefix
 				n, total := pref.Mask.Size()
diff --git a/setup_test.go b/setup_test.go
index b3f5c8d..3acae9b 100644
--- a/setup_test.go
+++ b/setup_test.go
@@ -10,58 +10,68 @@ func TestSetupDns64(t *testing.T) {
 	tests := []struct {
 		inputUpstreams string
 		shouldErr      bool
+		prefix         string
 	}{
 		{
 			`dns64`,
 			false,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
     upstream 8.8.8.8
 }`,
 			false,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
     prefix 64:ff9b::/96
 }`,
 			false,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
     prefix 64:ff9b::/32
 }`,
 			false,
+			"64:ff9b::/32",
 		},
 		{
 			`dns64 {
     prefix 64:ff9b::/52
 }`,
 			true,
+			"64:ff9b::/52",
 		},
 		{
 			`dns64 {
     prefix 64:ff9b::/104
 }`,
 			true,
+			"64:ff9b::/104",
 		},
 		{
 			`dns64 {
     prefix 8.8.8.8/24
 }`,
 			true,
+			"8.8.9.9/24",
 		},
 		{
 			`dns64 {
     upstream 8.8.8.8 8.8.4.4
 }`,
 			false,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
     upstream some_not_useable_domain
 }`,
 			true,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
@@ -69,6 +79,23 @@ func TestSetupDns64(t *testing.T) {
     upstream 8.8.8.8
 }`,
 			false,
+			"64:ff9b::/96",
+		},
+		{
+			`dns64 {
+    prefix 2002:ac12:b083::/96
+    upstream 8.8.8.8
+}`,
+			false,
+			"2002:ac12:b083::/96",
+		},
+		{
+			`dns64 {
+    prefix 2002:c0a8:a88a::/48
+    upstream 8.8.8.8
+}`,
+			false,
+			"2002:c0a8:a88a::/48",
 		},
 		{
 			`dns64 foobar {
@@ -76,24 +103,32 @@ func TestSetupDns64(t *testing.T) {
     upstream 8.8.8.8
 }`,
 			true,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 foobar`,
 			true,
+			"64:ff9b::/96",
 		},
 		{
 			`dns64 {
     foobar
 }`,
 			true,
+			"64:ff9b::/96",
 		},
 	}
 
 	for i, test := range tests {
 		c := caddy.NewTestController("dns", test.inputUpstreams)
-		_, _, err := dns64Parse(c)
+		_, pref, err := dns64Parse(c)
 		if (err != nil) != test.shouldErr {
 			t.Errorf("Test %d expected %v error, got %v for %s", i+1, test.shouldErr, err, test.inputUpstreams)
 		}
+		if err == nil {
+			if pref.String() != test.prefix {
+				t.Errorf("Test %d expected prefix %s, got %v", i+1, test.prefix, pref.String())
+			}
+		}
 	}
 }