diff --git a/src/_pytask/collect.py b/src/_pytask/collect.py
index 7fd1dff92..d0773988d 100644
--- a/src/_pytask/collect.py
+++ b/src/_pytask/collect.py
@@ -194,6 +194,8 @@ def pytask_collect_task(
     if (name.startswith("task_") or has_mark(obj, "task")) and callable(obj):
         dependencies = parse_nodes(session, path, name, obj, depends_on)
         products = parse_nodes(session, path, name, obj, produces)
+        if products == {}:
+            raise Exception("Tasks need to declare products.")
 
         markers = obj.pytask_meta.markers if hasattr(obj, "pytask_meta") else []
         kwargs = obj.pytask_meta.kwargs if hasattr(obj, "pytask_meta") else {}
diff --git a/tests/test_collect.py b/tests/test_collect.py
index 9a10831a5..e69d65db0 100644
--- a/tests/test_collect.py
+++ b/tests/test_collect.py
@@ -270,3 +270,11 @@ def test_find_shortest_uniquely_identifiable_names_for_tasks(tmp_path):
 
     result = _find_shortest_uniquely_identifiable_name_for_tasks(tasks)
     assert result == expected
+
+
+def test_task_has_no_produces_defined(tmp_path):
+    source = "def task_write_text(produces): pass"
+    tmp_path.joinpath("task_module.py").write_text(source)
+    session = main({"paths": tmp_path})
+    assert session.collection_reports[0].outcome == CollectionOutcome.FAILED
+    assert session.collection_reports[0].exc_info