diff --git a/debug_toolbar/apps.py b/debug_toolbar/apps.py
index ffae34209..614ce98f7 100644
--- a/debug_toolbar/apps.py
+++ b/debug_toolbar/apps.py
@@ -177,7 +177,7 @@ def check_panels(app_configs, **kwargs):
     return errors
 
 
-@register()
+@register
 def js_mimetype_check(app_configs, **kwargs):
     """
     Check that JavaScript files are resolving to the correct content type.
@@ -208,7 +208,7 @@ def js_mimetype_check(app_configs, **kwargs):
     return []
 
 
-@register()
+@register
 def debug_toolbar_installed_when_running_tests_check(app_configs, **kwargs):
     """
     Check that the toolbar is not being used when tests are running
@@ -223,13 +223,14 @@ def debug_toolbar_installed_when_running_tests_check(app_configs, **kwargs):
                 "the toolbar when running tests. If you feel this check is in error, "
                 "you can set `DEBUG_TOOLBAR_CONFIG['IS_RUNNING_TESTS'] = False` to "
                 "bypass this check.",
-                id="debug_toolbar.W008",
+                id="debug_toolbar.W009",
             )
         ]
     else:
         return []
 
 
+@register
 def check_settings(app_configs, **kwargs):
     errors = []
     USER_CONFIG = getattr(settings, "DEBUG_TOOLBAR_CONFIG", {})
diff --git a/docs/changes.rst b/docs/changes.rst
index 959d42dde..7a737231f 100644
--- a/docs/changes.rst
+++ b/docs/changes.rst
@@ -22,6 +22,8 @@ Pending
   ``DEBUG_TOOLBAR_SETTINGS``.
 * Add a note on the profiling panel about using Python 3.12 and later
   about needing ``--nothreading``
+* Fixed the bug causing ``'djdt' is not a registered namespace`` and updated
+  docs to help in initial configuration while running tests.
 
 4.3.0 (2024-02-01)
 ------------------
diff --git a/tests/test_checks.py b/tests/test_checks.py
index 6362d47b0..1718fa4c6 100644
--- a/tests/test_checks.py
+++ b/tests/test_checks.py
@@ -101,16 +101,6 @@ def test_panels_is_empty(self):
                     "settings.py.",
                     id="debug_toolbar.W005",
                 ),
-                Error(
-                    "The Django Debug Toolbar can't be used with tests",
-                    hint="Django changes the DEBUG setting to False when running "
-                    "tests. By default the Django Debug Toolbar is installed because "
-                    "DEBUG is set to True. For most cases, you need to avoid installing "
-                    "the toolbar when running tests. If you feel this check is in error, "
-                    "you can set `DEBUG_TOOLBAR_CONFIG['IS_RUNNING_TESTS'] = False` to "
-                    "bypass this check.",
-                    id="debug_toolbar.W008",
-                ),
             ],
         )
 
@@ -276,13 +266,16 @@ def test_debug_toolbar_installed_when_running_tests(self):
                         "the toolbar when running tests. If you feel this check is in error, "
                         "you can set `DEBUG_TOOLBAR_CONFIG['IS_RUNNING_TESTS'] = False` to "
                         "bypass this check.",
-                        id="debug_toolbar.W008",
+                        id="debug_toolbar.W009",
                     )
                 ],
             )
 
     @override_settings(
-        DEBUG_TOOLBAR_CONFIG={"OBSERVE_REQUEST_CALLBACK": lambda request: False}
+        DEBUG_TOOLBAR_CONFIG={
+            "OBSERVE_REQUEST_CALLBACK": lambda request: False,
+            "IS_RUNNING_TESTS": False,
+        }
     )
     def test_observe_request_callback_specified(self):
         errors = run_checks()