diff --git a/debian/changelog b/debian/changelog
index 675ef67..eb00d63 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -14,6 +14,7 @@ ubuntu-dev-tools (0.102) UNRELEASED; urgency=low
   * syncpackage:
     - Don't upload orig tarball if not needed.
     - Print error message if the download fails (LP: #639899).
+    - Check if the specified Debian component is valid (LP: #639896).
   * update-maintainer: Don't change the Maintainer field if the email is set
     to a @lists.ubuntu.com address.
   * sponsor-patch: New script to download a patch from a Launchpad bug, patch
@@ -37,7 +38,7 @@ ubuntu-dev-tools (0.102) UNRELEASED; urgency=low
   * Fix NAME section of lp-set-dup(1).
   * lp-list-bugs: New tool.
 
- -- Benjamin Drung <bdrung@ubuntu.com>  Sun, 19 Sep 2010 22:07:52 +0200
+ -- Benjamin Drung <bdrung@ubuntu.com>  Mon, 20 Sep 2010 00:42:35 +0200
 
 ubuntu-dev-tools (0.101) unstable; urgency=low
 
diff --git a/syncpackage b/syncpackage
index 48b27c6..22bd373 100755
--- a/syncpackage
+++ b/syncpackage
@@ -400,7 +400,7 @@ if __name__ == "__main__":
 	parser.add_option("-V", "--debian-version",
 			help="Specify the version to sync from.", dest="debversion", default=None)
 	parser.add_option("-c", "--component",
-			help="Specify the component to sync from.", dest="component", default=None)
+			help="Specify the Debian component to sync from.", dest="component", default=None)
 	parser.add_option("-v", "--verbose", help="print more information",
 			dest="verbose", action="store_true", default=False)
 	parser.add_option("-n", "--uploader-name", dest="uploader_name",
@@ -441,6 +441,11 @@ if __name__ == "__main__":
 	if args[0].endswith(".dsc"):
 		dscurl = args[0]
 	else:
+		if options.component not in (None, "main", "contrib", "non-free"):
+			print >> sys.stderr, "%s: Error: %s is not a valid Debian component." \
+					" It should be one of main, contrib, or non-free." % \
+					(script_name, options.component)
+			sys.exit(1)
 		dscurl = get_debian_dscurl(args[0], options.dist, options.release,
 				options.debversion, options.component)