diff --git a/src/Transport.ts b/src/Transport.ts
index 4dd2b14..8433de2 100644
--- a/src/Transport.ts
+++ b/src/Transport.ts
@@ -727,5 +727,5 @@ export function lowerCaseHeaders (oldHeaders?: http.IncomingHttpHeaders): http.I
  */
 function retryBackoff (min: number, max: number, attempt: number): number {
   const ceiling = Math.min(max, 2 ** attempt) / 2
-  return ceiling + ((Math.random() * (ceiling - min)) - min)
+  return ceiling + ((Math.random() * (ceiling - min)) + min)
 }