diff --git a/test/test_utils.py b/test/test_utils.py
index 2e3a6480c..b93503820 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -16,10 +16,12 @@ import json
 import xml.etree.ElementTree
 
 from youtube_dl.utils import (
+    add_defaults_if_directory,
     age_restricted,
     args_to_str,
     clean_html,
     DateRange,
+    DEFAULT_OUTTMPL,
     detect_exe_version,
     encodeFilename,
     escape_rfc3986,
@@ -581,6 +583,16 @@ ffmpeg version 2.4.4 Copyright (c) 2000-2014 the FFmpeg ...'''), '2.4.4')
             'like_count > 100 & dislike_count <? 50 & description',
             {'like_count': 190, 'dislike_count': 10}))
 
+    def test_add_defaults_if_directory(self):
+        cwd = os.getcwd()
+
+        existant_dir = os.path.join(cwd, '')  # ensure trailing slash
+        self.assertTrue(os.path.isdir(existant_dir))
+        self.assertEqual(add_defaults_if_directory(cwd), os.path.join(existant_dir, DEFAULT_OUTTMPL))
+
+        nonexistant_dir = os.path.join(cwd, 'add_defaults_if_directory_test')
+        self.assertFalse(os.path.isdir(nonexistant_dir))
+        self.assertEqual(add_defaults_if_directory(nonexistant_dir), nonexistant_dir)
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index 5b2c3aa38..eed033ee0 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -38,6 +38,7 @@ from .compat import (
     compat_urllib_request,
 )
 from .utils import (
+    add_defaults_if_directory,
     escape_url,
     ContentTooShortError,
     date_from_str,
@@ -567,6 +568,7 @@ class YoutubeDL(object):
 
             outtmpl = sanitize_path(self.params.get('outtmpl', DEFAULT_OUTTMPL))
             tmpl = compat_expanduser(outtmpl)
+            tmpl = add_defaults_if_directory(tmpl)
             filename = tmpl % template_dict
             # Temporary fix for #4787
             # 'Treat' all problem characters by passing filename through preferredencoding
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index edeee1853..7d8f3921c 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -325,6 +325,13 @@ def sanitize_path(s):
         sanitized_path.insert(0, drive_or_unc + os.path.sep)
     return os.path.join(*sanitized_path)
 
+def add_defaults_if_directory(path):
+    """Appends the default output template, if the given path is an existing directory.  Non-directory inputs are returned unchanged."""
+    if os.path.isdir(path):
+        dir = os.path.join(path, '')  # ensure trailing slash
+        return dir + DEFAULT_OUTTMPL
+    else:
+        return path
 
 def sanitize_url_path_consecutive_slashes(url):
     """Collapses consecutive slashes in URLs' path"""