diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index 18b1443b8..09d2b18f2 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -46,6 +46,7 @@ from .utils import (
     DateRange,
     DEFAULT_OUTTMPL,
     determine_ext,
+    determine_protocol,
     DownloadError,
     encode_compat_str,
     encodeFilename,
@@ -1309,6 +1310,10 @@ class YoutubeDL(object):
             # Automatically determine file extension if missing
             if 'ext' not in format:
                 format['ext'] = determine_ext(format['url']).lower()
+            # Automatically determine protocol if missing (useful for format
+            # selection purposes)
+            if 'protocol' not in format:
+                format['protocol'] = determine_protocol(format)
             # Add HTTP headers, so that external programs can use them from the
             # json output
             full_format_info = info_dict.copy()