diff --git a/src/lighteval/main_inspect.py b/src/lighteval/main_inspect.py
index 4aa5cbf87..97fccc191 100644
--- a/src/lighteval/main_inspect.py
+++ b/src/lighteval/main_inspect.py
@@ -435,7 +435,7 @@ def eval(  # noqa C901
 ):
     from lighteval.tasks.registry import Registry
 
-    registry = Registry(tasks=tasks, custom_tasks=None, load_multilingual=False)
+    registry = Registry(tasks=tasks, custom_tasks=custom_tasks, load_multilingual=False)
     task_configs = registry.task_to_configs
     inspect_ai_tasks = []
 
diff --git a/tests/unit/test_main_inspect.py b/tests/unit/test_main_inspect.py
new file mode 100644
index 000000000..598082744
--- /dev/null
+++ b/tests/unit/test_main_inspect.py
@@ -0,0 +1,57 @@
+# MIT License
+
+# Copyright (c) 2024 The HuggingFace Team
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+from unittest.mock import MagicMock, patch
+
+from lighteval.main_inspect import eval
+
+
+# Shared with slow tests: a real custom tasks module that defines gsm8k_test.
+CUSTOM_TASKS_PATH = "examples/custom_tasks_tests.py"
+
+
+def test_inspect_eval_forwards_custom_tasks_to_registry():
+    """Inspect eval must load tasks from the custom_tasks argument.
+
+    Without forwarding custom_tasks into Registry, a task that exists only in
+    the custom module cannot be resolved.
+    """
+    seen_configs = []
+
+    def capture_get_inspect_ai_task(task_config, epochs=1, epochs_reducer=None):
+        seen_configs.append(task_config)
+        return MagicMock(name=f"inspect-task-{task_config.name}")
+
+    with (
+        patch("lighteval.main_inspect.get_inspect_ai_task", side_effect=capture_get_inspect_ai_task),
+        patch("lighteval.main_inspect.inspect_ai_eval_set", return_value=(True, [])),
+    ):
+        eval(
+            models=["mock-model"],
+            tasks="gsm8k_test|0",
+            custom_tasks=CUSTOM_TASKS_PATH,
+            log_dir="unused-log-dir",
+        )
+
+    assert any(config.name == "gsm8k_test" for config in seen_configs), (
+        "Registry did not load the custom task; custom_tasks was likely ignored"
+    )