diff --git a/oauth2_test.go b/oauth2_test.go
index 2f7d731..a99d7a3 100644
--- a/oauth2_test.go
+++ b/oauth2_test.go
@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"reflect"
 	"strconv"
 	"testing"
@@ -170,6 +171,54 @@ func TestExchangeRequest_JSONResponse(t *testing.T) {
 	if scope != "user" {
 		t.Errorf("Unexpected value for scope: %v", scope)
 	}
+	expiresIn := tok.Extra("expires_in")
+	if expiresIn != float64(86400) {
+		t.Errorf("Unexpected non-numeric value for expires_in: %v", expiresIn)
+	}
+}
+
+func TestExtraValueRetrieval(t *testing.T) {
+	values := url.Values{}
+
+	kvmap := map[string]string{
+		"scope": "user", "token_type": "bearer", "expires_in": "86400.92",
+		"server_time": "1443571905.5606415", "referer_ip": "10.0.0.1",
+		"etag": "\"afZYj912P4alikMz_P11982\"", "request_id": "86400",
+		"untrimmed": "  untrimmed  ",
+	}
+
+	for key, value := range kvmap {
+		values.Set(key, value)
+	}
+
+	tok := Token{
+		raw: values,
+	}
+
+	scope := tok.Extra("scope")
+	if scope != "user" {
+		t.Errorf("Unexpected scope %v wanted \"user\"", scope)
+	}
+	serverTime := tok.Extra("server_time")
+	if serverTime != 1443571905.5606415 {
+		t.Errorf("Unexpected non-float64 value for server_time: %v", serverTime)
+	}
+	refererIp := tok.Extra("referer_ip")
+	if refererIp != "10.0.0.1" {
+		t.Errorf("Unexpected non-string value for referer_ip: %v", refererIp)
+	}
+	expires_in := tok.Extra("expires_in")
+	if expires_in != 86400.92 {
+		t.Errorf("Unexpected value for expires_in, wanted 86400 got %v", expires_in)
+	}
+	requestId := tok.Extra("request_id")
+	if requestId != int64(86400) {
+		t.Errorf("Unexpected non-int64 value for request_id: %v", requestId)
+	}
+	untrimmed := tok.Extra("untrimmed")
+	if untrimmed != "  untrimmed  " {
+		t.Errorf("Unexpected value for untrimmed, got %q expected \"  untrimmed \"", untrimmed)
+	}
 }
 
 const day = 24 * time.Hour
diff --git a/token.go b/token.go
index ebbdddb..4e596f0 100644
--- a/token.go
+++ b/token.go
@@ -7,6 +7,7 @@ package oauth2
 import (
 	"net/http"
 	"net/url"
+	"strconv"
 	"strings"
 	"time"
 
@@ -92,14 +93,28 @@ func (t *Token) WithExtra(extra interface{}) *Token {
 // Extra fields are key-value pairs returned by the server as a
 // part of the token retrieval response.
 func (t *Token) Extra(key string) interface{} {
-	if vals, ok := t.raw.(url.Values); ok {
-		// TODO(jbd): Cast numeric values to int64 or float64.
-		return vals.Get(key)
-	}
 	if raw, ok := t.raw.(map[string]interface{}); ok {
 		return raw[key]
 	}
-	return nil
+
+	vals, ok := t.raw.(url.Values)
+	if !ok {
+		return nil
+	}
+
+	v := vals.Get(key)
+	switch s := strings.TrimSpace(v); strings.Count(s, ".") {
+	case 0: // Contains no "."; try to parse as int
+		if i, err := strconv.ParseInt(s, 10, 64); err == nil {
+			return i
+		}
+	case 1: // Contains a single "."; try to parse as float
+		if f, err := strconv.ParseFloat(s, 64); err == nil {
+			return f
+		}
+	}
+
+	return v
 }
 
 // expired reports whether the token is expired.
diff --git a/token_test.go b/token_test.go
index 739eeb2..8344329 100644
--- a/token_test.go
+++ b/token_test.go
@@ -41,6 +41,7 @@ func TestTokenExpiry(t *testing.T) {
 	}{
 		{name: "12 seconds", tok: &Token{Expiry: now.Add(12 * time.Second)}, want: false},
 		{name: "10 seconds", tok: &Token{Expiry: now.Add(expiryDelta)}, want: true},
+		{name: "-1 hour", tok: &Token{Expiry: now.Add(-1 * time.Hour)}, want: true},
 	}
 	for _, tc := range cases {
 		if got, want := tc.tok.expired(), tc.want; got != want {
@@ -48,3 +49,24 @@ func TestTokenExpiry(t *testing.T) {
 		}
 	}
 }
+
+func TestTokenTypeMethod(t *testing.T) {
+	cases := []struct {
+		name string
+		tok  *Token
+		want string
+	}{
+		{name: "bearer-mixed_case", tok: &Token{TokenType: "beAREr"}, want: "Bearer"},
+		{name: "default-bearer", tok: &Token{}, want: "Bearer"},
+		{name: "basic", tok: &Token{TokenType: "basic"}, want: "Basic"},
+		{name: "basic-capitalized", tok: &Token{TokenType: "Basic"}, want: "Basic"},
+		{name: "mac", tok: &Token{TokenType: "mac"}, want: "MAC"},
+		{name: "mac-caps", tok: &Token{TokenType: "MAC"}, want: "MAC"},
+		{name: "mac-mixed_case", tok: &Token{TokenType: "mAc"}, want: "MAC"},
+	}
+	for _, tc := range cases {
+		if got, want := tc.tok.Type(), tc.want; got != want {
+			t.Errorf("TokenType(%q) = %v; want %v", tc.name, got, want)
+		}
+	}
+}