diff --git a/README.md b/README.md
index f015dbc..23ac0e8 100644
--- a/README.md
+++ b/README.md
@@ -191,7 +191,7 @@ The above command pulled the existing data out of Route53 and placed the results
 | [EnvVarSource](/octodns/source/envvar.py) | | TXT | No | read-only environment variable injection |
 | [GoogleCloudProvider](/octodns/provider/googlecloud.py) | google-cloud-dns | A, AAAA, CAA, CNAME, MX, NAPTR, NS, PTR, SPF, SRV, TXT  | No | |
 | [MythicBeastsProvider](/octodns/provider/mythicbeasts.py) | Mythic Beasts | A, AAAA, ALIAS, CNAME, MX, NS, SRV, SSHFP, CAA, TXT | No | |
-| [Ns1Provider](/octodns/provider/ns1.py) | ns1-python | All | Yes | No CNAME support, missing `NA` geo target |
+| [Ns1Provider](/octodns/provider/ns1.py) | ns1-python | All | Yes | Missing `NA` geo target |
 | [OVH](/octodns/provider/ovh.py) | ovh | A, AAAA, CAA, CNAME, MX, NAPTR, NS, PTR, SPF, SRV, SSHFP, TXT, DKIM | No | |
 | [PowerDnsProvider](/octodns/provider/powerdns.py) | | All | No | |
 | [Rackspace](/octodns/provider/rackspace.py) | | A, AAAA, ALIAS, CNAME, MX, NS, PTR, SPF, TXT | No |  |
diff --git a/octodns/cmds/sync.py b/octodns/cmds/sync.py
index 60793e7..dbf4103 100755
--- a/octodns/cmds/sync.py
+++ b/octodns/cmds/sync.py
@@ -25,18 +25,19 @@ def main():
     parser.add_argument('zone', nargs='*', default=[],
                         help='Limit sync to the specified zone(s)')
 
-    # --sources isn't an option here b/c filtering sources out would be super
-    # dangerous since you could easily end up with an empty zone and delete
-    # everything, or even just part of things when there are multiple sources
-
+    parser.add_argument('--source', default=[], action='append',
+                        help='Limit sync to zones with the specified '
+                        'source(s) (all sources will be synchronized for the '
+                        'selected zones)')
     parser.add_argument('--target', default=[], action='append',
                         help='Limit sync to the specified target(s)')
 
     args = parser.parse_args()
 
     manager = Manager(args.config_file)
-    manager.sync(eligible_zones=args.zone, eligible_targets=args.target,
-                 dry_run=not args.doit, force=args.force)
+    manager.sync(eligible_zones=args.zone, eligible_sources=args.source,
+                 eligible_targets=args.target, dry_run=not args.doit,
+                 force=args.force)
 
 
 if __name__ == '__main__':
diff --git a/octodns/manager.py b/octodns/manager.py
index 0665938..288645f 100644
--- a/octodns/manager.py
+++ b/octodns/manager.py
@@ -255,8 +255,8 @@ class Manager(object):
 
         return plans
 
-    def sync(self, eligible_zones=[], eligible_targets=[], dry_run=True,
-             force=False):
+    def sync(self, eligible_zones=[], eligible_sources=[], eligible_targets=[],
+             dry_run=True, force=False):
         self.log.info('sync: eligible_zones=%s, eligible_targets=%s, '
                       'dry_run=%s, force=%s', eligible_zones, eligible_targets,
                       dry_run, force)
@@ -280,6 +280,12 @@ class Manager(object):
             except KeyError:
                 raise ManagerException('Zone {} is missing targets'
                                        .format(zone_name))
+
+            if (eligible_sources and not
+                    [s for s in sources if s in eligible_sources]):
+                self.log.info('sync:   no eligible sources, skipping')
+                continue
+
             if eligible_targets:
                 targets = [t for t in targets if t in eligible_targets]
 
diff --git a/requirements.txt b/requirements.txt
index dd1643f..24f57ff 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,14 +1,14 @@
 PyYaml==5.3.1
 azure-common==1.1.25
 azure-mgmt-dns==3.0.0
-boto3==1.14.14
-botocore==1.17.14
+boto3==1.14.52
+botocore==1.17.52
 dnspython==1.16.0
 docutils==0.16
 dyn==1.8.1
 edgegrid-python==1.1.1
 futures==3.2.0; python_version < '3.2'
-google-cloud-core==1.3.0
+google-cloud-core==1.4.1
 google-cloud-dns==0.32.0
 ipaddress==1.0.23; python_version < '3.3'
 jmespath==0.10.0
@@ -17,7 +17,7 @@ natsort==6.2.1
 ns1-python==0.16.0
 ovh==0.5.0
 pycountry-convert==0.7.2
-pycountry==19.8.18
+pycountry==20.7.3
 python-dateutil==2.8.1
 requests==2.24.0
 s3transfer==0.3.3
diff --git a/tests/test_octodns_manager.py b/tests/test_octodns_manager.py
index 581689a..9956790 100644
--- a/tests/test_octodns_manager.py
+++ b/tests/test_octodns_manager.py
@@ -151,6 +151,14 @@ class TestManager(TestCase):
                 .sync(dry_run=False, force=True)
             self.assertEquals(25, tc)
 
+    def test_eligible_sources(self):
+        with TemporaryDirectory() as tmpdir:
+            environ['YAML_TMP_DIR'] = tmpdir.dirname
+            # Only allow a target that doesn't exist
+            tc = Manager(get_config_filename('simple.yaml')) \
+                .sync(eligible_sources=['foo'])
+            self.assertEquals(0, tc)
+
     def test_eligible_targets(self):
         with TemporaryDirectory() as tmpdir:
             environ['YAML_TMP_DIR'] = tmpdir.dirname