diff --git a/pipenv/utils.py b/pipenv/utils.py
index a19f7ed0f6..8188ee4316 100644
--- a/pipenv/utils.py
+++ b/pipenv/utils.py
@@ -180,12 +180,18 @@ def __init__(self, python_version, python_path):
         self.python_path = python_path
 
     def __enter__(self):
-        os.environ['PIP_PYTHON_VERSION'] = str(self.python_version)
-        os.environ['PIP_PYTHON_PATH'] = str(self.python_path)
+        # Only inject when the value is valid
+        if self.python_version:
+            os.environ['PIP_PYTHON_VERSION'] = str(self.python_version)
+        if self.python_path:
+            os.environ['PIP_PYTHON_PATH'] = str(self.python_path)
 
     def __exit__(self, *args):
         # Restore original Python version information.
-        del os.environ['PIP_PYTHON_VERSION']
+        try:
+            del os.environ['PIP_PYTHON_VERSION']
+        except KeyError:
+            pass
 
 
 def prepare_pip_source_args(sources, pip_args=None):
diff --git a/tests/integration/test_lock.py b/tests/integration/test_lock.py
index 0dfd22bb41..705e62a6d0 100644
--- a/tests/integration/test_lock.py
+++ b/tests/integration/test_lock.py
@@ -1,5 +1,6 @@
 import pytest
 import os
+import six
 
 from pipenv.utils import temp_environ
 
@@ -331,7 +332,7 @@ def test_lock_updated_source(PipenvInstance, pypi):
 @pytest.mark.lock
 @pytest.mark.vcs
 @pytest.mark.needs_internet
-def lock_editable_vcs_without_install(PipenvInstance, pypi):
+def test_lock_editable_vcs_without_install(PipenvInstance, pypi):
     with PipenvInstance(pypi=pypi, chdir=True) as p:
         with open(p.pipfile_path, 'w') as f:
             f.write("""
@@ -345,3 +346,17 @@ def lock_editable_vcs_without_install(PipenvInstance, pypi):
         assert 'chardet' in p.lockfile['default']
         c = p.pipenv('install')
         assert c.return_code == 0
+
+
+@pytest.mark.lock
+def test_lock_respecting_python_version(PipenvInstance, pypi):
+    with PipenvInstance(pypi=pypi) as p:
+        with open(p.pipfile_path, 'w') as f:
+            f.write("""
+[packages]
+django = "*"
+            """.strip())
+        django_version = '==2.0.6' if six.PY3 else '==1.11.10'
+        c = p.pipenv('lock')
+        assert c.return_code == 0
+        assert p.lockfile['default']['django']['version'] == django_version
diff --git a/tests/pypi/django/Django-2.0.6.tar.gz b/tests/pypi/django/Django-2.0.6.tar.gz
new file mode 100644
index 0000000000..bc69557b4f
Binary files /dev/null and b/tests/pypi/django/Django-2.0.6.tar.gz differ