diff --git a/gclient.py b/gclient.py
index a5567365b..7dd3a6c80 100755
--- a/gclient.py
+++ b/gclient.py
@@ -2002,7 +2002,7 @@ def CMDsync(parser, args):
   parser.add_option('-m', '--manually_grab_svn_rev', action='store_true',
                     help='DEPRECATED: This is a no-op.')
   # TODO(phajdan.jr): Remove validation options once default (crbug/570091).
-  parser.add_option('--validate-syntax', action='store_true',
+  parser.add_option('--validate-syntax', action='store_true', default=True,
                     help='Validate the .gclient and DEPS syntax')
   parser.add_option('--disable-syntax-validation', action='store_false',
                     dest='validate_syntax',