diff --git a/util.go b/util.go
index 1f8616f..0c16095 100644
--- a/util.go
+++ b/util.go
@@ -23,6 +23,12 @@ func makeURLValues(v interface{}) (url.Values, error) {
 
 		fieldValue := valElem.Field(i)
 
+		stringer, ok := fieldValue.Interface().(fmt.Stringer)
+		if ok {
+			values.Set(urlTag, stringer.String())
+			continue
+		}
+
 		k := fieldValue.Kind()
 		var s string
 		switch k {
diff --git a/util_internal_test.go b/util_internal_test.go
index 639c604..171df5a 100644
--- a/util_internal_test.go
+++ b/util_internal_test.go
@@ -1,20 +1,24 @@
 package luno
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func TestMakeURLValues(t *testing.T) {
 
 	type S string
 
 	type Req struct {
-		S   string  `url:"s"`
-		I   int     `url:"i"`
-		I64 int64   `url:"i64"`
-		F32 float32 `url:"f32"`
-		F64 float64 `url:"f64"`
-		B   bool    `url:"b"`
-		ABy []byte  `url:"aby"`
-		TS  S       `url:"ts"`
+		S   string    `url:"s"`
+		I   int       `url:"i"`
+		I64 int64     `url:"i64"`
+		F32 float32   `url:"f32"`
+		F64 float64   `url:"f64"`
+		B   bool      `url:"b"`
+		ABy []byte    `url:"aby"`
+		TS  S         `url:"ts"`
+		T   time.Time `url:"t"` // implements fmt.Stringer
 	}
 
 	r := Req{
@@ -26,6 +30,7 @@ func TestMakeURLValues(t *testing.T) {
 		B:   true,
 		ABy: []byte("foo"),
 		TS:  S("foo"),
+		T:   time.Date(2018, 1, 1, 0, 0, 0, 0, time.UTC),
 	}
 
 	v, err := makeURLValues(&r)
@@ -33,7 +38,7 @@ func TestMakeURLValues(t *testing.T) {
 		t.Errorf("Expected success, got %v", err)
 		return
 	}
-	exp := "aby=foo&b=true&f32=42.4200&f64=42.4200&i=42&i64=42&s=foo&ts=foo"
+	exp := "aby=foo&b=true&f32=42.4200&f64=42.4200&i=42&i64=42&s=foo&t=2018-01-01+00%3A00%3A00+%2B0000+UTC&ts=foo"
 	act := v.Encode()
 	if act != exp {
 		t.Errorf("Expected %q, got %q", exp, act)