diff --git a/python/pyspark/sql/tests.py b/python/pyspark/sql/tests.py
index 83899ad4b1b12..2720439416682 100644
--- a/python/pyspark/sql/tests.py
+++ b/python/pyspark/sql/tests.py
@@ -24,6 +24,7 @@
 import pydoc
 import shutil
 import tempfile
+import pickle
 
 import py4j
 
@@ -88,6 +89,14 @@ def __eq__(self, other):
             other.x == self.x and other.y == self.y
 
 
+class DataTypeTests(unittest.TestCase):
+    # regression test for SPARK-6055
+    def test_data_type_eq(self):
+        lt = LongType()
+        lt2 = pickle.loads(pickle.dumps(LongType()))
+        self.assertEquals(lt, lt2)
+
+
 class SQLTests(ReusedPySparkTestCase):
 
     @classmethod
diff --git a/python/pyspark/sql/types.py b/python/pyspark/sql/types.py
index 3e7c1256f3595..31a861e1feb46 100644
--- a/python/pyspark/sql/types.py
+++ b/python/pyspark/sql/types.py
@@ -509,22 +509,23 @@ def __eq__(self, other):
 def _parse_datatype_json_string(json_string):
     """Parses the given data type JSON string.
     >>> import pickle
-    >>> LongType() == pickle.loads(pickle.dumps(LongType()))
-    True
     >>> def check_datatype(datatype):
+    ...     pickled = pickle.loads(pickle.dumps(datatype))
+    ...     assert datatype == pickled
     ...     scala_datatype = sqlCtx._ssql_ctx.parseDataType(datatype.json())
     ...     python_datatype = _parse_datatype_json_string(scala_datatype.json())
-    ...     return datatype == python_datatype
-    >>> all(check_datatype(cls()) for cls in _all_primitive_types.values())
-    True
+    ...     assert datatype == python_datatype
+    >>> for cls in _all_primitive_types.values():
+    ...     check_datatype(cls())
+
     >>> # Simple ArrayType.
     >>> simple_arraytype = ArrayType(StringType(), True)
     >>> check_datatype(simple_arraytype)
-    True
+
     >>> # Simple MapType.
     >>> simple_maptype = MapType(StringType(), LongType())
     >>> check_datatype(simple_maptype)
-    True
+
     >>> # Simple StructType.
     >>> simple_structtype = StructType([
     ...     StructField("a", DecimalType(), False),
@@ -532,7 +533,7 @@ def _parse_datatype_json_string(json_string):
     ...     StructField("c", LongType(), True),
     ...     StructField("d", BinaryType(), False)])
     >>> check_datatype(simple_structtype)
-    True
+
     >>> # Complex StructType.
     >>> complex_structtype = StructType([
     ...     StructField("simpleArray", simple_arraytype, True),
@@ -541,22 +542,20 @@ def _parse_datatype_json_string(json_string):
     ...     StructField("boolean", BooleanType(), False),
     ...     StructField("withMeta", DoubleType(), False, {"name": "age"})])
     >>> check_datatype(complex_structtype)
-    True
+
     >>> # Complex ArrayType.
     >>> complex_arraytype = ArrayType(complex_structtype, True)
     >>> check_datatype(complex_arraytype)
-    True
+
     >>> # Complex MapType.
     >>> complex_maptype = MapType(complex_structtype,
     ...                           complex_arraytype, False)
     >>> check_datatype(complex_maptype)
-    True
+
     >>> check_datatype(ExamplePointUDT())
-    True
     >>> structtype_with_udt = StructType([StructField("label", DoubleType(), False),
     ...                                   StructField("point", ExamplePointUDT(), False)])
     >>> check_datatype(structtype_with_udt)
-    True
     """
     return _parse_datatype_json_value(json.loads(json_string))