diff --git a/scrapy/command/cmdline.py b/scrapy/command/cmdline.py
index d900a537c..c0e4a6ad2 100644
--- a/scrapy/command/cmdline.py
+++ b/scrapy/command/cmdline.py
@@ -61,6 +61,8 @@ def usage(prog):
     return s
 
 def update_default_settings(module, cmdname):
+    if not module:
+        return
     try:
         mod = __import__('%s.%s' % (module, cmdname), {}, {}, [''])
     except ImportError: