--- a/jupyter_core/tests/test_command.py
+++ b/jupyter_core/tests/test_command.py
@@ -131,7 +131,7 @@ def test_not_on_path(tmpdir):
     witness_src = '#!%s\n%s\n' % (sys.executable, 'print("WITNESS ME")')
     write_executable(witness, witness_src)

-    env = {'PATH': ''}
+    env = {'PATH': '', 'PYTHONPATH': os.environ['PYTHONPATH']}
     if 'SYSTEMROOT' in os.environ:  # Windows http://bugs.python.org/issue20614
         env[str('SYSTEMROOT')] = os.environ['SYSTEMROOT']
     if sys.platform == 'win32':
@@ -157,7 +157,7 @@ def test_path_priority(tmpdir):
     witness_b_src = '#!%s\n%s\n' % (sys.executable, 'print("WITNESS B")')
     write_executable(witness_b, witness_b_src)

-    env = {'PATH':  str(b)}
+    env = {'PATH':  str(b), 'PYTHONPATH': os.environ['PYTHONPATH']}
     if 'SYSTEMROOT' in os.environ:  # Windows http://bugs.python.org/issue20614
         env[str('SYSTEMROOT')] = os.environ['SYSTEMROOT']
     if sys.platform == 'win32':