diff --git a/google/internal/externalaccount/sts_exchange.go b/google/internal/externalaccount/sts_exchange.go
index a8a704b..e6fcae5 100644
--- a/google/internal/externalaccount/sts_exchange.go
+++ b/google/internal/externalaccount/sts_exchange.go
@@ -65,6 +65,9 @@ func exchangeToken(ctx context.Context, endpoint string, request *stsTokenExchan
 	defer resp.Body.Close()
 
 	body, err := ioutil.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return nil, err
+	}
 	if c := resp.StatusCode; c < 200 || c > 299 {
 		return nil, fmt.Errorf("oauth2/google: status code %d: %s", c, body)
 	}