diff --git a/internal/token.go b/internal/token.go
index a3460eb..17746d6 100644
--- a/internal/token.go
+++ b/internal/token.go
@@ -49,6 +49,13 @@ type Token struct {
 	// mechanisms for that TokenSource will not be used.
 	Expiry time.Time
 
+	// ExpiresIn is the OAuth2 wire format "expires_in" field,
+	// which specifies how many seconds later the token expires,
+	// relative to an unknown time base approximately around "now".
+	// It is the application's responsibility to populate
+	// `Expiry` from `ExpiresIn` when required.
+	ExpiresIn int64 `json:"expires_in,omitempty"`
+
 	// Raw optionally contains extra metadata from the server
 	// when updating a token.
 	Raw interface{}
@@ -311,6 +318,7 @@ func doTokenRoundTrip(ctx context.Context, req *http.Request) (*Token, error) {
 			TokenType:    tj.TokenType,
 			RefreshToken: tj.RefreshToken,
 			Expiry:       tj.expiry(),
+			ExpiresIn:    int64(tj.ExpiresIn),
 			Raw:          make(map[string]interface{}),
 		}
 		json.Unmarshal(body, &token.Raw) // no error checks for optional fields
diff --git a/token.go b/token.go
index 8c31136..bb7545e 100644
--- a/token.go
+++ b/token.go
@@ -163,6 +163,7 @@ func tokenFromInternal(t *internal.Token) *Token {
 		TokenType:    t.TokenType,
 		RefreshToken: t.RefreshToken,
 		Expiry:       t.Expiry,
+		ExpiresIn:    t.ExpiresIn,
 		raw:          t.Raw,
 	}
 }