diff --git a/superset/models/core.py b/superset/models/core.py
index d0a32a1864c2b..0b78d50b62bf7 100755
--- a/superset/models/core.py
+++ b/superset/models/core.py
@@ -703,9 +703,14 @@ def get_pk_constraint(
         self, table_name: str, schema: Optional[str] = None
     ) -> Dict[str, Any]:
         pk_constraint = self.inspector.get_pk_constraint(table_name, schema) or {}
-        return {
-            key: utils.base_json_conv(value) for key, value in pk_constraint.items()
-        }
+
+        def _convert(value: Any) -> Any:
+            try:
+                return utils.base_json_conv(value)
+            except TypeError:
+                return None
+
+        return {key: _convert(value) for key, value in pk_constraint.items()}
 
     def get_foreign_keys(
         self, table_name: str, schema: Optional[str] = None
diff --git a/superset/utils/core.py b/superset/utils/core.py
index a893696e024f3..3d482c1c37b8d 100644
--- a/superset/utils/core.py
+++ b/superset/utils/core.py
@@ -556,9 +556,16 @@ def format_timedelta(time_delta: timedelta) -> str:
     return str(time_delta)
 
 
-def base_json_conv(  # pylint: disable=inconsistent-return-statements
-    obj: Any,
-) -> Any:
+def base_json_conv(obj: Any) -> Any:
+    """
+    Tries to convert additional types to JSON compatible forms.
+
+    :param obj: The serializable object
+    :returns: The JSON compatible form
+    :raises TypeError: If the object cannot be serialized
+    :see: https://docs.python.org/3/library/json.html#encoders-and-decoders
+    """
+
     if isinstance(obj, memoryview):
         obj = obj.tobytes()
     if isinstance(obj, np.int64):
@@ -581,47 +588,60 @@ def base_json_conv(  # pylint: disable=inconsistent-return-statements
         except Exception:  # pylint: disable=broad-except
             return "[bytes]"
 
+    raise TypeError(f"Unserializable object {obj} of type {type(obj)}")
+
 
-def json_iso_dttm_ser(obj: Any, pessimistic: bool = False) -> str:
+def json_iso_dttm_ser(obj: Any, pessimistic: bool = False) -> Any:
     """
-    json serializer that deals with dates
+    A JSON serializer that deals with dates by serializing them to ISO 8601.
 
-    >>> dttm = datetime(1970, 1, 1)
-    >>> json.dumps({'dttm': dttm}, default=json_iso_dttm_ser)
-    '{"dttm": "1970-01-01T00:00:00"}'
+        >>> json.dumps({'dttm': datetime(1970, 1, 1)}, default=json_iso_dttm_ser)
+        '{"dttm": "1970-01-01T00:00:00"}'
+
+    :param obj: The serializable object
+    :param pessimistic: Whether to be pessimistic regarding serialization
+    :returns: The JSON compatible form
+    :raises TypeError: If the non-pessimistic object cannot be serialized
     """
-    val = base_json_conv(obj)
-    if val is not None:
-        return val
+
     if isinstance(obj, (datetime, date, pd.Timestamp)):
-        obj = obj.isoformat()
-    else:
+        return obj.isoformat()
+
+    try:
+        return base_json_conv(obj)
+    except TypeError as ex:
         if pessimistic:
-            return "Unserializable [{}]".format(type(obj))
+            return f"Unserializable [{type(obj)}]"
 
-        raise TypeError("Unserializable object {} of type {}".format(obj, type(obj)))
-    return obj
+        raise ex
 
 
-def pessimistic_json_iso_dttm_ser(obj: Any) -> str:
+def pessimistic_json_iso_dttm_ser(obj: Any) -> Any:
     """Proxy to call json_iso_dttm_ser in a pessimistic way
 
     If one of object is not serializable to json, it will still succeed"""
     return json_iso_dttm_ser(obj, pessimistic=True)
 
 
-def json_int_dttm_ser(obj: Any) -> float:
-    """json serializer that deals with dates"""
-    val = base_json_conv(obj)
-    if val is not None:
-        return val
+def json_int_dttm_ser(obj: Any) -> Any:
+    """
+    A JSON serializer that deals with dates by serializing them to EPOCH.
+
+        >>> json.dumps({'dttm': datetime(1970, 1, 1)}, default=json_int_dttm_ser)
+        '{"dttm": 0.0}'
+
+    :param obj: The serializable object
+    :returns: The JSON compatible form
+    :raises TypeError: If the object cannot be serialized
+    """
+
     if isinstance(obj, (datetime, pd.Timestamp)):
-        obj = datetime_to_epoch(obj)
-    elif isinstance(obj, date):
-        obj = (obj - EPOCH.date()).total_seconds() * 1000
-    else:
-        raise TypeError("Unserializable object {} of type {}".format(obj, type(obj)))
-    return obj
+        return datetime_to_epoch(obj)
+
+    if isinstance(obj, date):
+        return (obj - EPOCH.date()).total_seconds() * 1000
+
+    return base_json_conv(obj)
 
 
 def json_dumps_w_dates(payload: Dict[Any, Any], sort_keys: bool = False) -> str:
diff --git a/tests/integration_tests/utils_tests.py b/tests/integration_tests/utils_tests.py
index 7df9cd82f96f0..a0614a1cd30a7 100644
--- a/tests/integration_tests/utils_tests.py
+++ b/tests/integration_tests/utils_tests.py
@@ -94,9 +94,10 @@ def test_json_int_dttm_ser(self):
         assert json_int_dttm_ser(datetime(1970, 1, 1)) == 0
         assert json_int_dttm_ser(date(1970, 1, 1)) == 0
         assert json_int_dttm_ser(dttm + timedelta(milliseconds=1)) == (ts + 1)
+        assert json_int_dttm_ser(np.int64(1)) == 1
 
         with self.assertRaises(TypeError):
-            json_int_dttm_ser("this is not a date")
+            json_int_dttm_ser(np.datetime64())
 
     def test_json_iso_dttm_ser(self):
         dttm = datetime(2020, 1, 1)
@@ -105,19 +106,31 @@ def test_json_iso_dttm_ser(self):
         assert json_iso_dttm_ser(dttm) == dttm.isoformat()
         assert json_iso_dttm_ser(dt) == dt.isoformat()
         assert json_iso_dttm_ser(t) == t.isoformat()
+        assert json_iso_dttm_ser(np.int64(1)) == 1
+
+        assert (
+            json_iso_dttm_ser(np.datetime64(), pessimistic=True)
+            == "Unserializable [<class 'numpy.datetime64'>]"
+        )
 
         with self.assertRaises(TypeError):
-            json_iso_dttm_ser("this is not a date")
+            json_iso_dttm_ser(np.datetime64())
 
     def test_base_json_conv(self):
-        assert isinstance(base_json_conv(np.bool_(1)), bool) is True
-        assert isinstance(base_json_conv(np.int64(1)), int) is True
-        assert isinstance(base_json_conv(np.array([1, 2, 3])), list) is True
-        assert isinstance(base_json_conv(set([1])), list) is True
-        assert isinstance(base_json_conv(Decimal("1.0")), float) is True
-        assert isinstance(base_json_conv(uuid.uuid4()), str) is True
-        assert isinstance(base_json_conv(time()), str) is True
-        assert isinstance(base_json_conv(timedelta(0)), str) is True
+        assert isinstance(base_json_conv(np.bool_(1)), bool)
+        assert isinstance(base_json_conv(np.int64(1)), int)
+        assert isinstance(base_json_conv(np.array([1, 2, 3])), list)
+        assert base_json_conv(np.array(None)) is None
+        assert isinstance(base_json_conv(set([1])), list)
+        assert isinstance(base_json_conv(Decimal("1.0")), float)
+        assert isinstance(base_json_conv(uuid.uuid4()), str)
+        assert isinstance(base_json_conv(time()), str)
+        assert isinstance(base_json_conv(timedelta(0)), str)
+        assert isinstance(base_json_conv(bytes()), str)
+        assert base_json_conv(bytes("", encoding="utf-16")) == "[bytes]"
+
+        with pytest.raises(TypeError):
+            base_json_conv(np.datetime64())
 
     def test_zlib_compression(self):
         json_str = '{"test": 1}'