diff --git a/UPDATING.md b/UPDATING.md
index a2662551cef26..7b0bc97aa0902 100644
--- a/UPDATING.md
+++ b/UPDATING.md
@@ -1,15 +1,24 @@
 # Updating Airflow
 
-This file aims to document the backwards-incompatible changes in Airflow and
-assist people with migrating to a new version.
+This file documents any backwards-incompatible changes in Airflow and
+assists people when migrating to a new version.
 
-## 1.7 to 1.8
 
-### DAGs now don't start automatically when created
+## Airflow 1.8
 
-To retain the old behavior, add this to your configuration:
+### Changes to Behavior
+
+#### New DAGs are paused by default
+
+Previously, new DAGs would be scheduled immediately. To retain the old behavior, add this to airflow.cfg:
 
 ```
+[core]
 dags_are_paused_at_creation = False
 ```
 
+### Deprecated Features
+These features are marked for deprecation. They may still work (and raise a `DeprecationWarning`), but are no longer supported and will be removed entirely in Airflow 2.0
+
+#### Operators no longer accept arbitrary arguments
+Previously, `Operator.__init__()` accepted any arguments (either positional `*args` or keyword `**kwargs`) without complaint. Now, invalid arguments will be rejected.
diff --git a/airflow/configuration.py b/airflow/configuration.py
index 64f31262e5ae3..dd8b633b92d84 100644
--- a/airflow/configuration.py
+++ b/airflow/configuration.py
@@ -8,6 +8,7 @@
 import logging
 import os
 import subprocess
+import warnings
 
 from future import standard_library
 standard_library.install_aliases()
@@ -16,6 +17,9 @@
 from collections import OrderedDict
 from configparser import ConfigParser
 
+# show DeprecationWarning and PendingDeprecationWarning
+warnings.simplefilter('default', DeprecationWarning)
+warnings.simplefilter('default', PendingDeprecationWarning)
 
 class AirflowConfigException(Exception):
     pass
diff --git a/airflow/example_dags/example_http_operator.py b/airflow/example_dags/example_http_operator.py
index 2e20516ffad95..bbfc17afe58c8 100644
--- a/airflow/example_dags/example_http_operator.py
+++ b/airflow/example_dags/example_http_operator.py
@@ -66,7 +66,7 @@
 
 sensor = HttpSensor(
     task_id='http_sensor_check',
-    conn_id='http_default',
+    http_conn_id='http_default',
     endpoint='',
     params={},
     response_check=lambda response: True if "Google" in response.content else False,
diff --git a/airflow/models.py b/airflow/models.py
index fd1349ecf5860..2cc51cc7b6705 100644
--- a/airflow/models.py
+++ b/airflow/models.py
@@ -37,6 +37,7 @@
 import socket
 import sys
 import traceback
+import warnings
 from urllib.parse import urlparse
 
 from sqlalchemy import (
@@ -1597,6 +1598,17 @@ def __init__(
             *args,
             **kwargs):
 
+        if args or kwargs:
+            # TODO remove *args and **kwargs in Airflow 2.0
+            warnings.warn(
+                'Invalid arguments were passed to {c}. Support for '
+                'passing such arguments will be dropped in Airflow 2.0.'
+                'Invalid arguments were:'
+                '\n*args: {a}\n**kwargs: {k}'.format(
+                    c=self.__class__.__name__, a=args, k=kwargs),
+                category=PendingDeprecationWarning
+            )
+
         validate_key(task_id)
         self.dag_id = dag.dag_id if dag else 'adhoc_' + owner
         self.task_id = task_id
diff --git a/airflow/utils/decorators.py b/airflow/utils/decorators.py
index 5568559699bb9..bc4678cc48db0 100644
--- a/airflow/utils/decorators.py
+++ b/airflow/utils/decorators.py
@@ -12,9 +12,17 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-import inspect
 import os
 
+# inspect.signature is only available in Python 3. funcsigs.signature is
+# a backport.
+try:
+    import inspect
+    signature = inspect.signature
+except AttributeError:
+    import funcsigs
+    signature = funcsigs.signature
+
 from copy import copy
 from functools import wraps
 
@@ -57,12 +65,14 @@ def wrapper(*args, **kwargs):
 
         dag_args.update(default_args)
         default_args = dag_args
-        arg_spec = inspect.getargspec(func)
-        num_defaults = len(arg_spec.defaults) if arg_spec.defaults else 0
-        non_optional_args = arg_spec.args[:-num_defaults]
-        if 'self' in non_optional_args:
-            non_optional_args.remove('self')
-        for arg in func.__code__.co_varnames:
+
+        sig = signature(func)
+        non_optional_args = [
+            name for (name, param) in sig.parameters.items()
+            if param.default == param.empty and
+            param.name != 'self' and
+            param.kind not in (param.VAR_POSITIONAL, param.VAR_KEYWORD)]
+        for arg in sig.parameters:
             if arg in default_args and arg not in kwargs:
                 kwargs[arg] = default_args[arg]
         missing_args = list(set(non_optional_args) - set(kwargs))
diff --git a/setup.py b/setup.py
index 924aa3245c394..4f708416435fa 100644
--- a/setup.py
+++ b/setup.py
@@ -122,6 +122,7 @@ def run(self):
         'flask-cache>=0.13.1, <0.14',
         'flask-login==0.2.11',
         'future>=0.15.0, <0.16',
+        'funcsigs>=0.4, <1'
         'gunicorn>=19.3.0, <19.4.0',  # 19.4.? seemed to have issues
         'jinja2>=2.7.3, <3.0',
         'markdown>=2.5.2, <3.0',
diff --git a/tests/core.py b/tests/core.py
index 484282fa964ad..373d35ebf075c 100644
--- a/tests/core.py
+++ b/tests/core.py
@@ -12,6 +12,7 @@
 from email.mime.application import MIMEApplication
 import signal
 from time import sleep
+import warnings
 
 from dateutil.relativedelta import relativedelta
 
@@ -320,6 +321,22 @@ def test_clear_api(self):
         ti = models.TaskInstance(task=task, execution_date=DEFAULT_DATE)
         ti.are_dependents_done()
 
+    def test_illegal_args(self):
+        """
+        Tests that Operators reject illegal arguments
+        """
+        with warnings.catch_warnings(record=True) as w:
+            t = operators.BashOperator(
+                task_id='test_illegal_args',
+                bash_command='echo success',
+                dag=self.dag,
+                illegal_argument_1234='hello?')
+            self.assertTrue(
+                issubclass(w[0].category, PendingDeprecationWarning))
+            self.assertIn(
+                'Invalid arguments were passed to BashOperator.',
+                w[0].message.args[0])
+
     def test_bash_operator(self):
         t = operators.BashOperator(
             task_id='time_sensor_check',