diff --git a/dataset/database.py b/dataset/database.py
index 3155b5a..87d85be 100644
--- a/dataset/database.py
+++ b/dataset/database.py
@@ -45,9 +45,9 @@ class Database(object):
                 if len(schema_qs):
                     schema = schema_qs.pop()
 
-        self.types = Types()
         self.schema = schema
         self.engine = create_engine(url, **engine_kwargs)
+        self.types = Types(self.engine.dialect.name)
         self.url = url
         self.row_type = row_type
         self.ensure_schema = ensure_schema
diff --git a/dataset/types.py b/dataset/types.py
index 46f5550..904ffa9 100644
--- a/dataset/types.py
+++ b/dataset/types.py
@@ -1,7 +1,7 @@
 from datetime import datetime, date
 
 from sqlalchemy import Integer, UnicodeText, Float, BigInteger
-from sqlalchemy import Boolean, Date, DateTime, Unicode
+from sqlalchemy import Boolean, Date, DateTime, Unicode, JSON
 from sqlalchemy.types import TypeEngine
 
 
@@ -16,22 +16,37 @@ class Types(object):
     date = Date
     datetime = DateTime
 
-    def guess(cls, sample):
+    def __init__(self, dialect = None):
+        self._dialect = dialect
+
+    @property
+    def json(self):
+        if self._dialect is not None and self._dialect == 'postgresql':
+            from sqlalchemy.dialects.postgresql import JSONB
+            return JSONB
+        return JSON
+
+    def guess(self, sample, dialect = None):
         """Given a single sample, guess the column type for the field.
 
         If the sample is an instance of an SQLAlchemy type, the type will be
         used instead.
         """
+        if dialect is not None:
+            self._dialect = dialect
+
         if isinstance(sample, TypeEngine):
             return sample
         if isinstance(sample, bool):
-            return cls.boolean
+            return self.boolean
         elif isinstance(sample, int):
-            return cls.bigint
+            return self.bigint
         elif isinstance(sample, float):
-            return cls.float
+            return self.float
         elif isinstance(sample, datetime):
-            return cls.datetime
+            return self.datetime
         elif isinstance(sample, date):
-            return cls.date
-        return cls.text
+            return self.date
+        elif isinstance(sample, dict):
+            return self.json
+        return self.text
diff --git a/test/test_dataset.py b/test/test_dataset.py
index e5cecd6..fb21952 100644
--- a/test/test_dataset.py
+++ b/test/test_dataset.py
@@ -192,6 +192,20 @@ class TableTestCase(unittest.TestCase):
             )
         assert len(self.tbl) == len(TEST_DATA) + 1, len(self.tbl)
 
+    def test_insert_json(self):
+        last_id = self.tbl.insert({
+            'date': datetime(2011, 1, 2),
+            'temperature': -10,
+            'place': 'Berlin',
+            'info': {
+                'currency': 'EUR',
+                'language': 'German',
+                'population': 3292365
+            }
+        })
+        assert len(self.tbl) == len(TEST_DATA) + 1, len(self.tbl)
+        assert self.tbl.find_one(id=last_id)['place'] == 'Berlin'
+
     def test_upsert(self):
         self.tbl.upsert({
             'date': datetime(2011, 1, 2),