diff --git a/youtube_dl/downloader/http.py b/youtube_dl/downloader/http.py
index 5ac132773..f9cd23a2d 100644
--- a/youtube_dl/downloader/http.py
+++ b/youtube_dl/downloader/http.py
@@ -227,7 +227,7 @@ class HttpFD(FileDownloader):
         now = None  # needed for slow_down() in the first loop run
         before = start  # start measuring
         peak_rate = 0
-        throttling_start = time.time()
+        throttling_start = None
         throttling_threshold = None
         throttling_start_size = 0
         while True: