diff --git a/CHANGELOG.md b/CHANGELOG.md
index 618883a7..3ec40f81 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- skip None values when merging extracted and rule items
+
 ### Security
 
 ## [0.47.0] - 2025-01-23
diff --git a/mex/common/merged/main.py b/mex/common/merged/main.py
index 07badfc5..8fef57a7 100644
--- a/mex/common/merged/main.py
+++ b/mex/common/merged/main.py
@@ -153,4 +153,5 @@ def create_merged_item(
     try:
         return cls.model_validate(merged_dict)
     except ValidationError as error:
-        raise MergingError from error
+        msg = "Could not validate merged model."
+        raise MergingError(msg) from error
diff --git a/mex/common/merged/utils.py b/mex/common/merged/utils.py
index e16a26e7..bacbe54c 100644
--- a/mex/common/merged/utils.py
+++ b/mex/common/merged/utils.py
@@ -4,20 +4,28 @@
 T = TypeVar("T")
 
 
-def extend_list_in_dict(dict_: dict[str, list[T]], key: str, item: list[T] | T) -> None:
+def extend_list_in_dict(
+    dict_: dict[str, list[T]], key: str, item: list[T] | T | None
+) -> None:
     """Extend a list in a dict for a given key with the given unique item(s)."""
     list_ = dict_.setdefault(key, [])
-    if not isinstance(item, list):
+    if item is None:
+        item = []
+    elif not isinstance(item, list):
         item = [item]
     for mergeable in item:
         if mergeable not in list_:
             list_.append(mergeable)
 
 
-def prune_list_in_dict(dict_: dict[str, list[T]], key: str, item: list[T] | T) -> None:
+def prune_list_in_dict(
+    dict_: dict[str, list[T]], key: str, item: list[T] | T | None
+) -> None:
     """Safely remove item(s) from a list in a dict for the given key."""
     list_ = dict_.setdefault(key, [])
-    if not isinstance(item, list):
+    if item is None:
+        item = []
+    elif not isinstance(item, list):
         item = [item]
     for removable in item:
         with contextlib.suppress(ValueError):
diff --git a/tests/merged/test_main.py b/tests/merged/test_main.py
index a4202674..67614eef 100644
--- a/tests/merged/test_main.py
+++ b/tests/merged/test_main.py
@@ -13,22 +13,27 @@
     ActivityRuleSetRequest,
     AdditiveOrganizationalUnit,
     AdditivePerson,
+    AdditiveResource,
     AnyExtractedModel,
     AnyRuleSetRequest,
     ContactPointRuleSetRequest,
     ExtractedActivity,
     ExtractedContactPoint,
     ExtractedPerson,
+    ExtractedResource,
     PersonRuleSetRequest,
     PreventiveContactPoint,
     PreventivePerson,
+    PreventiveResource,
+    ResourceRuleSetRequest,
     SubtractiveActivity,
     SubtractiveContactPoint,
     SubtractiveOrganizationalUnit,
     SubtractivePerson,
+    SubtractiveResource,
 )
 from mex.common.testing import Joker
-from mex.common.types import Identifier, Text, TextLanguage
+from mex.common.types import AccessRestriction, Identifier, Text, TextLanguage, Theme
 
 
 def test_merge_extracted_items_and_apply_preventive_rule() -> None:
@@ -121,6 +126,34 @@ def test_apply_subtractive_rule() -> None:
 @pytest.mark.parametrize(
     ("extracted_items", "rule_set", "validate_cardinality", "expected"),
     [
+        (
+            [
+                ExtractedResource(
+                    identifierInPrimarySource="r1",
+                    hadPrimarySource=Identifier.generate(seed=42),
+                    accessRestriction=AccessRestriction["OPEN"],
+                    contact=[Identifier.generate(seed=999)],
+                    unitInCharge=[Identifier.generate(seed=999)],
+                    theme=[Theme["PUBLIC_HEALTH"]],
+                    title=[Text(value="Dummy resource")],
+                )
+            ],
+            ResourceRuleSetRequest(
+                additive=AdditiveResource(),
+                subtractive=SubtractiveResource(),
+                preventive=PreventiveResource(),
+            ),
+            True,
+            {
+                "accessRestriction": "https://mex.rki.de/item/access-restriction-1",
+                "contact": ["bFQoRhcVH5DIax"],
+                "theme": ["https://mex.rki.de/item/theme-1"],
+                "title": [{"value": "Dummy resource", "language": TextLanguage.EN}],
+                "unitInCharge": ["bFQoRhcVH5DIax"],
+                "entityType": "MergedResource",
+                "identifier": "bFQoRhcVH5DHU6",
+            },
+        ),
         (
             [
                 ExtractedPerson(
@@ -295,6 +328,7 @@ def test_apply_subtractive_rule() -> None:
         ),
     ],
     ids=(
+        "single extracted item",
         "extracted items and rule set",
         "only rule set",
         "only extracted items",
diff --git a/tests/merged/test_utils.py b/tests/merged/test_utils.py
index ca55de7d..5af5117e 100644
--- a/tests/merged/test_utils.py
+++ b/tests/merged/test_utils.py
@@ -16,9 +16,28 @@ def test_extend_list_in_dict() -> None:
         "new-key": ["single-value"],
     }
 
+    extend_list_in_dict(dict_, "existing-key", None)
+    assert dict_ == {
+        "existing-key": ["already-here", "another-value"],
+        "new-key": ["single-value"],
+    }
+
+    extend_list_in_dict(dict_, "another-key", None)
+    assert dict_ == {
+        "existing-key": ["already-here", "another-value"],
+        "new-key": ["single-value"],
+        "another-key": [],
+    }
+
 
 def test_prune_list_in_dict() -> None:
     dict_ = {
+        "existing-key": ["leave-me-alone"],
+        "prune-me": ["1", "2", "42", "foo"],
+    }
+
+    prune_list_in_dict(dict_, "prune-me", ["1", "2"])
+    assert dict_ == {
         "existing-key": ["leave-me-alone"],
         "prune-me": ["42", "foo"],
     }
@@ -29,6 +48,12 @@ def test_prune_list_in_dict() -> None:
         "prune-me": ["42"],
     }
 
+    prune_list_in_dict(dict_, "prune-me", None)
+    assert dict_ == {
+        "existing-key": ["leave-me-alone"],
+        "prune-me": ["42"],
+    }
+
     prune_list_in_dict(dict_, "does-not-exist", "42")
     assert dict_ == {
         "existing-key": ["leave-me-alone"],