diff --git a/octodns/record.py b/octodns/record.py
index 6517d74..60a3686 100644
--- a/octodns/record.py
+++ b/octodns/record.py
@@ -406,6 +406,22 @@ class _DynamicPool(object):
         return '{}'.format(self.data)
 
 
+class _DynamicRuleGeo(object):
+    geo_re = re.compile(r'^(?P<continent_code>\w\w)(-(?P<country_code>\w\w)'
+                        r'(-(?P<subdivision_code>\w\w))?)?$')
+
+    @classmethod
+    def validate(cls, rule_num, code):
+        reasons = []
+        # TODO: ideally this would validate the actual code...
+        match = cls.geo_re.match(code)
+        if not match:
+            reasons.append('rule {} invalid geo "{}"'.format(rule_num, code))
+        return reasons
+
+    # TODO: flesh this out
+
+
 class _DynamicRule(object):
 
     def __init__(self, i, data):
@@ -517,6 +533,8 @@ class _DynamicMixin(object):
         elif not rules:
             reasons.append('missing rules')
         else:
+            seen_default = False
+
             for rule_num, rule in enumerate(rules):
                 rule_num += 1
                 try:
@@ -532,7 +550,21 @@ class _DynamicMixin(object):
                     reasons.append('rule {} undefined pool "{}"'
                                    .format(rule_num, pool))
 
-                # TODO: validate GEOs if present
+                try:
+                    geos = rule['geos']
+                except KeyError:
+                    geos = []
+                    if seen_default:
+                        reasons.append('rule {} duplicate default'
+                                       .format(rule_num))
+                    seen_default = True
+
+                if not isinstance(geos, (list, tuple)):
+                    reasons.append('rule {} geos must be a list'
+                                   .format(rule_num))
+                else:
+                    for geo in geos:
+                        reasons.extend(_DynamicRuleGeo.validate(rule_num, geo))
 
         return reasons
 
diff --git a/tests/config/dynamic.tests.yaml b/tests/config/dynamic.tests.yaml
index ac83ad5..c48735e 100644
--- a/tests/config/dynamic.tests.yaml
+++ b/tests/config/dynamic.tests.yaml
@@ -21,9 +21,11 @@ a:
           - value: 5.5.5.5
             weight: 25
     rules:
-      - geo: EU-UK
+      - geos:
+        - EU-UK
         pool: iad
-      - geo: EU
+      - geos:
+        - EU
         pool: ams
       - geos:
           - NA-US-CA
@@ -55,9 +57,11 @@ aaaa:
           - value: 2601:642:500:e210:62f8:1dff:feb8:9476
             weight: 2
     rules:
-      - geo: EU-UK
+      - geos:
+        - EU-UK
         pool: iad
-      - geo: EU
+      - geos:
+        - EU
         pool: ams
       - geos:
           - NA-US-CA
@@ -88,9 +92,11 @@ cname:
           - value: target-sea-2.unit.tests.
             weight: 175
     rules:
-      - geo: EU-UK
+      - geos:
+        - EU-UK
         pool: iad
-      - geo: EU
+      - geos:
+        - EU
         pool: ams
       - geos:
           - NA-US-CA
diff --git a/tests/test_octodns_record.py b/tests/test_octodns_record.py
index 0a4e4df..45853d7 100644
--- a/tests/test_octodns_record.py
+++ b/tests/test_octodns_record.py
@@ -2688,6 +2688,113 @@ class TestDynamicRecords(TestCase):
         self.assertEquals(["rule 1 undefined pool \"non-existant\""],
                           ctx.exception.reasons)
 
+        # rule with invalid geos
+        a_data = {
+            'dynamic': {
+                'pools': {
+                    'one': {
+                        'values': [{
+                            'value': '3.3.3.3',
+                        }]
+                    },
+                    'two': {
+                        'values': [{
+                            'value': '4.4.4.4',
+                        }, {
+                            'value': '5.5.5.5',
+                        }]
+                    },
+                },
+                'rules': [{
+                    'geos': 'NA-US-CA',
+                    'pool': 'two',
+                }, {
+                    'pool': 'one',
+                }],
+            },
+            'ttl': 60,
+            'type': 'A',
+            'values': [
+                '1.1.1.1',
+                '2.2.2.2',
+            ],
+        }
+        with self.assertRaises(ValidationError) as ctx:
+            Record.new(self.zone, 'bad', a_data)
+        self.assertEquals(['rule 1 geos must be a list'],
+                          ctx.exception.reasons)
+
+        # rule with invalid geo
+        a_data = {
+            'dynamic': {
+                'pools': {
+                    'one': {
+                        'values': [{
+                            'value': '3.3.3.3',
+                        }]
+                    },
+                    'two': {
+                        'values': [{
+                            'value': '4.4.4.4',
+                        }, {
+                            'value': '5.5.5.5',
+                        }]
+                    },
+                },
+                'rules': [{
+                    'geos': ['invalid'],
+                    'pool': 'two',
+                }, {
+                    'pool': 'one',
+                }],
+            },
+            'ttl': 60,
+            'type': 'A',
+            'values': [
+                '1.1.1.1',
+                '2.2.2.2',
+            ],
+        }
+        with self.assertRaises(ValidationError) as ctx:
+            Record.new(self.zone, 'bad', a_data)
+        self.assertEquals(['rule 1 invalid geo "invalid"'],
+                          ctx.exception.reasons)
+
+        # multiple default rules
+        a_data = {
+            'dynamic': {
+                'pools': {
+                    'one': {
+                        'values': [{
+                            'value': '3.3.3.3',
+                        }]
+                    },
+                    'two': {
+                        'values': [{
+                            'value': '4.4.4.4',
+                        }, {
+                            'value': '5.5.5.5',
+                        }]
+                    },
+                },
+                'rules': [{
+                    'pool': 'two',
+                }, {
+                    'pool': 'one',
+                }],
+            },
+            'ttl': 60,
+            'type': 'A',
+            'values': [
+                '1.1.1.1',
+                '2.2.2.2',
+            ],
+        }
+        with self.assertRaises(ValidationError) as ctx:
+            Record.new(self.zone, 'bad', a_data)
+        self.assertEquals(['rule 2 duplicate default'],
+                          ctx.exception.reasons)
+
     def test_dynamic_lenient(self):
         # Missing pools
         a_data = {