diff --git a/tests/conftest.py b/tests/conftest.py
index 09b76ed..acc46fa 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -39,8 +39,6 @@ manifest:
     path: zephyr
 '''
 
-WEST_SKIP_SLOW_TESTS = bool(int(os.environ.get('WEST_SKIP_SLOW_TESTS', 1)))
-
 WINDOWS = (platform.system() == 'Windows')
 
 #
diff --git a/tests/test_manifest.py b/tests/test_manifest.py
index 4419639..67472bf 100644
--- a/tests/test_manifest.py
+++ b/tests/test_manifest.py
@@ -26,8 +26,7 @@ from west.manifest import Manifest, Project, ManifestProject, \
     _ManifestImportDepth, is_group
 
 from conftest import create_workspace, create_repo, checkout_branch, \
-    create_branch, add_commit, rev_parse, GIT, check_proj_consistency, \
-    WEST_SKIP_SLOW_TESTS
+    create_branch, add_commit, rev_parse, GIT, check_proj_consistency
 
 FPI = ImportFlag.FORCE_PROJECTS  # to force project imports to use the callback
 
@@ -2405,8 +2404,6 @@ def test_import_path_prefix_no_escape(manifest_repo):
         MF(topdir=topdir, import_flags=ImportFlag.IGNORE)
     assert 'escapes the workspace topdir' in str(excinfo.value)
 
-@pytest.mark.skipif(WEST_SKIP_SLOW_TESTS,
-                    reason='use WEST_SKIP_SLOW_TESTS=0 to enable')
 def test_import_loop_detection_self(manifest_repo):
     # Verify that a self-import which causes an import loop is an error.
 
diff --git a/tox.ini b/tox.ini
index 602e1db..ad1b431 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,7 +26,6 @@ deps =
     mypy
 setenv =
     TOXTEMPDIR={envtmpdir}
-passenv = WEST_SKIP_SLOW_TESTS
 commands =
   python -m flake8 --config={toxinidir}/tox.ini {toxinidir}
   python -m mypy --config-file={toxinidir}/tox.ini --package=west