diff --git a/compose/config/config.py b/compose/config/config.py
index 055ae18ac..98b825ec2 100644
--- a/compose/config/config.py
+++ b/compose/config/config.py
@@ -512,12 +512,12 @@ def resolve_environment(service_dict):
         env.update(env_vars_from_file(env_file))
 
     env.update(parse_environment(service_dict.get('environment')))
-    return dict(filter(None, (resolve_env_var(k, v) for k, v in six.iteritems(env))))
+    return dict(resolve_env_var(k, v) for k, v in six.iteritems(env))
 
 
 def resolve_build_args(build):
     args = parse_build_arguments(build.get('args'))
-    return dict(filter(None, (resolve_env_var(k, v) for k, v in six.iteritems(args))))
+    return dict(resolve_env_var(k, v) for k, v in six.iteritems(args))
 
 
 def validate_extended_service_dict(service_dict, filename, service):
@@ -827,7 +827,7 @@ def resolve_env_var(key, val):
     elif key in os.environ:
         return key, os.environ[key]
     else:
-        return ()
+        return key, ''
 
 
 def env_vars_from_file(filename):
diff --git a/tests/integration/service_test.py b/tests/integration/service_test.py
index bcb873354..129d996d9 100644
--- a/tests/integration/service_test.py
+++ b/tests/integration/service_test.py
@@ -916,6 +916,7 @@ class ServiceTest(DockerClientTestCase):
             'FILE_DEF': 'F1',
             'FILE_DEF_EMPTY': '',
             'ENV_DEF': 'E3',
+            'NO_DEF': ''
         }.items():
             self.assertEqual(env[k], v)
 
diff --git a/tests/unit/config/config_test.py b/tests/unit/config/config_test.py
index 4d3bb7be7..446fc5600 100644
--- a/tests/unit/config/config_test.py
+++ b/tests/unit/config/config_test.py
@@ -1975,7 +1975,7 @@ class EnvTest(unittest.TestCase):
         }
         self.assertEqual(
             resolve_environment(service_dict),
-            {'FILE_DEF': 'F1', 'FILE_DEF_EMPTY': '', 'ENV_DEF': 'E3'},
+            {'FILE_DEF': 'F1', 'FILE_DEF_EMPTY': '', 'ENV_DEF': 'E3', 'NO_DEF': ''},
         )
 
     def test_resolve_environment_from_env_file(self):
@@ -2016,6 +2016,7 @@ class EnvTest(unittest.TestCase):
                 'FILE_DEF': u'bär',
                 'FILE_DEF_EMPTY': '',
                 'ENV_DEF': 'E3',
+                'NO_DEF': ''
             },
         )
 
@@ -2034,7 +2035,7 @@ class EnvTest(unittest.TestCase):
         }
         self.assertEqual(
             resolve_build_args(build),
-            {'arg1': 'value1', 'empty_arg': '', 'env_arg': 'value2'},
+            {'arg1': 'value1', 'empty_arg': '', 'env_arg': 'value2', 'no_env': ''},
         )
 
     @pytest.mark.xfail(IS_WINDOWS_PLATFORM, reason='paths use slash')