diff --git a/jupyter_core/tests/test_command.py b/jupyter_core/tests/test_command.py
index 4ef38cd..08fba22 100644
--- a/jupyter_core/tests/test_command.py
+++ b/jupyter_core/tests/test_command.py
@@ -174,7 +174,7 @@ def test_not_on_path(tmpdir):
     witness_src = "#!{}\n{}\n".format(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["SYSTEMROOT"] = os.environ["SYSTEMROOT"]
     if sys.platform == "win32":
@@ -198,7 +198,7 @@ def test_path_priority(tmpdir):
     witness_b_src = "#!{}\n{}\n".format(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["SYSTEMROOT"] = os.environ["SYSTEMROOT"]
     if sys.platform == "win32":