diff --git a/subcmds/sync.py b/subcmds/sync.py
index 3eab2fc..5655a1e 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -738,36 +738,30 @@
       fd.close()
     return 0
 
-  def Execute(self, opt, args):
-    if opt.jobs:
-      self.jobs = opt.jobs
-    if self.jobs > 1:
-      soft_limit, _ = _rlimit_nofile()
-      self.jobs = min(self.jobs, (soft_limit - 5) // 3)
-
+  def ValidateOptions(self, opt, args):
     if opt.force_broken:
       print('warning: -f/--force-broken is now the default behavior, and the '
             'options are deprecated', file=sys.stderr)
     if opt.network_only and opt.detach_head:
-      print('error: cannot combine -n and -d', file=sys.stderr)
-      sys.exit(1)
+      self.OptionParser.error('cannot combine -n and -d')
     if opt.network_only and opt.local_only:
-      print('error: cannot combine -n and -l', file=sys.stderr)
-      sys.exit(1)
+      self.OptionParser.error('cannot combine -n and -l')
     if opt.manifest_name and opt.smart_sync:
-      print('error: cannot combine -m and -s', file=sys.stderr)
-      sys.exit(1)
+      self.OptionParser.error('cannot combine -m and -s')
     if opt.manifest_name and opt.smart_tag:
-      print('error: cannot combine -m and -t', file=sys.stderr)
-      sys.exit(1)
+      self.OptionParser.error('cannot combine -m and -t')
     if opt.manifest_server_username or opt.manifest_server_password:
       if not (opt.smart_sync or opt.smart_tag):
-        print('error: -u and -p may only be combined with -s or -t',
-              file=sys.stderr)
-        sys.exit(1)
+        self.OptionParser.error('-u and -p may only be combined with -s or -t')
       if None in [opt.manifest_server_username, opt.manifest_server_password]:
-        print('error: both -u and -p must be given', file=sys.stderr)
-        sys.exit(1)
+        self.OptionParser.error('both -u and -p must be given')
+
+  def Execute(self, opt, args):
+    if opt.jobs:
+      self.jobs = opt.jobs
+    if self.jobs > 1:
+      soft_limit, _ = _rlimit_nofile()
+      self.jobs = min(self.jobs, (soft_limit - 5) // 3)
 
     if opt.manifest_name:
       self.manifest.Override(opt.manifest_name)