diff --git a/src/caosdb/apiutils.py b/src/caosdb/apiutils.py
index 4c8393111bcbb4f9f91e309b81bebdcac55ba626..e378b39f85650dc7506e12977337f854e790e0e2 100644
--- a/src/caosdb/apiutils.py
+++ b/src/caosdb/apiutils.py
@@ -338,11 +338,13 @@ def merge_entities(entity_a: Entity, entity_b: Entity):
                 raise NotImplementedError()
 
             for attribute in ("datatype", "unit", "value"):
-                if diff_r1["properties"][key][attribute] is None:
-                    setattr(entity_a.get_property(key), attribute,
-                            diff_r2["properties"][key][attribute])
-                else:
-                    raise RuntimeError("Merge conflict.")
+                if (attribute in diff_r2["properties"][key] and
+                        diff_r2["properties"][key][attribute] is not None):
+                    if (diff_r1["properties"][key][attribute] is None):
+                        setattr(entity_a.get_property(key), attribute,
+                                diff_r2["properties"][key][attribute])
+                    else:
+                        raise RuntimeError("Merge conflict.")
         else:
             # TODO: This is a temporary FIX for
             #       https://gitlab.indiscale.com/caosdb/src/caosdb-pylib/-/issues/105
diff --git a/unittests/test_apiutils.py b/unittests/test_apiutils.py
index 43ab8107183f16bf8df1d0ea8e447b378bcf8123..2ebdf95a3aa5ce76b983b2c3c47630e1a8884705 100644
--- a/unittests/test_apiutils.py
+++ b/unittests/test_apiutils.py
@@ -296,6 +296,19 @@ def test_merge_entities():
     assert r2.get_property("F").value == "text"
 
 
+def test_merge_bug_conflict():
+    r = db.Record()
+    r.add_property(name="C", value=4)
+    r2 = db.Record()
+    r2.add_property(name="C", value=4, datatype="TEXT")
+    merge_entities(r, r2)
+
+    r3 = db.Record()
+    r3.add_property(name="C", value=4, datatype="INTEGER")
+    with pytest.raises(RuntimeError) as excinfo:
+        merge_entities(r3, r2)
+
+
 def test_merge_bug_109():
     rt = db.RecordType(name="TestBug")
     p = db.Property(name="test_bug_property", datatype=db.LIST(db.INTEGER))