diff --git a/compose/config/environment.py b/compose/config/environment.py
index 696356f3246..0d9c28ba392 100644
--- a/compose/config/environment.py
+++ b/compose/config/environment.py
@@ -19,17 +19,11 @@
 def split_env(env):
     if isinstance(env, six.binary_type):
         env = env.decode('utf-8', 'replace')
-    key = value = None
+
     if '=' in env:
         key, value = env.split('=', 1)
     else:
-        key = env
-    if re.search(r'\s', key):
-        raise ConfigurationError(
-            "environment variable name '{}' may not contain whitespace.".format(key)
-        )
-    return key, value
-
+        return env, None
 
 def env_vars_from_file(filename):
     """
diff --git a/tests/unit/config/environment_test.py b/tests/unit/config/environment_test.py
index 88eb0d6e11a..66e1eb123bc 100644
--- a/tests/unit/config/environment_test.py
+++ b/tests/unit/config/environment_test.py
@@ -53,12 +53,3 @@ def test_env_vars_from_file_bom(self):
         assert env_vars_from_file(str(tmpdir.join('bom.env'))) == {
             'PARK_BOM': '박봄'
         }
-
-    def test_env_vars_from_file_whitespace(self):
-        tmpdir = pytest.ensuretemp('env_file')
-        self.addCleanup(tmpdir.remove)
-        with codecs.open('{}/whitespace.env'.format(str(tmpdir)), 'w', encoding='utf-8') as f:
-            f.write('WHITESPACE =yes\n')
-        with pytest.raises(ConfigurationError) as exc:
-            env_vars_from_file(str(tmpdir.join('whitespace.env')))
-        assert 'environment variable' in exc.exconly()