diff --git a/openedx_learning/apps/authoring/containers/api.py b/openedx_learning/apps/authoring/containers/api.py
index 065c8a01..f4ee44b8 100644
--- a/openedx_learning/apps/authoring/containers/api.py
+++ b/openedx_learning/apps/authoring/containers/api.py
@@ -298,7 +298,7 @@ def create_next_container_version(
 
     * Something was added to the Container.
     * We re-ordered the rows in the container.
-    * Something was removed to the container.
+    * Something was removed from the container.
     * The Container's metadata changed, e.g. the title.
     * We pin to different versions of the Container.
 
diff --git a/tests/openedx_learning/apps/authoring/units/test_api.py b/tests/openedx_learning/apps/authoring/units/test_api.py
index 26170aca..67097af0 100644
--- a/tests/openedx_learning/apps/authoring/units/test_api.py
+++ b/tests/openedx_learning/apps/authoring/units/test_api.py
@@ -3,6 +3,8 @@
 """
 import pytest
 
+from django.core.exceptions import ValidationError
+
 from ..components.test_api import ComponentTestCase
 from openedx_learning.api import authoring as authoring_api
 from openedx_learning.api import authoring_models
@@ -105,6 +107,30 @@ def test_create_unit_with_invalid_children(self):
         # Check that a new version was not created:
         assert unit.versioning.draft == unit_version
 
+    def test_adding_external_components(self):
+        """
+        Test that components from another learning package cannot be added to a
+        unit.
+        """
+        learning_package2 = authoring_api.create_learning_package(key="other-package", title="Other Package")
+        unit, _unit_version = authoring_api.create_unit_and_version(
+            learning_package_id=learning_package2.pk,
+            key=f"unit:key",
+            title="Unit",
+            created=self.now,
+            created_by=None,
+        )
+        assert self.component_1.learning_package != learning_package2
+        # Try adding a a component from LP 1 (self.learning_package) to a unit from LP 2
+        with pytest.raises(ValidationError, match="Container entities must be from the same learning package."):
+            authoring_api.create_next_unit_version(
+                unit=unit,
+                title="Unit Containing an External Component",
+                components=[self.component_1],
+                created=self.now,
+                created_by=None,
+            )
+
     def test_create_empty_unit_and_version(self):
         """Test creating a unit with no components.