diff --git a/src/ifcopenshell-python/ifcopenshell/api/resource/assign_resource.py b/src/ifcopenshell-python/ifcopenshell/api/resource/assign_resource.py
index 8ba19a650d..32f9f2ced9 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/resource/assign_resource.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/resource/assign_resource.py
@@ -81,7 +81,7 @@ def assign_resource(
     """
     if related_object.HasAssignments:
         for assignment in related_object.HasAssignments:
-            if assignment.is_a("IfclRelAssignsToResource") and assignment.RelatingResource == relating_resource:
+            if assignment.is_a("IfcRelAssignsToResource") and assignment.RelatingResource == relating_resource:
                 return assignment
 
     resource_of = None
diff --git a/src/ifcopenshell-python/test/api/resource/test_assign_resource.py b/src/ifcopenshell-python/test/api/resource/test_assign_resource.py
new file mode 100644
index 0000000000..9c8ce2c2a4
--- /dev/null
+++ b/src/ifcopenshell-python/test/api/resource/test_assign_resource.py
@@ -0,0 +1,45 @@
+# IfcOpenShell - IFC toolkit and geometry engine
+# Copyright (C) 2024 Dion Moult <dion@thinkmoult.com>
+#
+# This file is part of IfcOpenShell.
+#
+# IfcOpenShell is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# IfcOpenShell is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
+
+import ifcopenshell.api.resource
+import ifcopenshell.api.root
+import test.bootstrap
+
+
+class TestAssignResource(test.bootstrap.IFC4):
+    def test_assigning_a_new_object_to_a_resource(self):
+        self.file.create_entity("IfcProject")
+        resource = ifcopenshell.api.resource.add_resource(self.file, ifc_class="IfcCrewResource")
+        actor = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcActor")
+        rel = ifcopenshell.api.resource.assign_resource(self.file, relating_resource=resource, related_object=actor)
+        assert rel.is_a("IfcRelAssignsToResource")
+        assert rel.RelatingResource == resource
+        assert rel.RelatedObjects == (actor,)
+
+    def test_assigning_the_same_object_twice_does_not_duplicate_related_objects(self):
+        # Regression test for #8203: a typo in the duplicate guard
+        # ("IfclRelAssignsToResource") meant the guard never matched, so a
+        # repeat assignment appended the related object to RelatedObjects again.
+        self.file.create_entity("IfcProject")
+        resource = ifcopenshell.api.resource.add_resource(self.file, ifc_class="IfcCrewResource")
+        actor = ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcActor")
+        rel1 = ifcopenshell.api.resource.assign_resource(self.file, relating_resource=resource, related_object=actor)
+        rel2 = ifcopenshell.api.resource.assign_resource(self.file, relating_resource=resource, related_object=actor)
+        assert rel1 == rel2
+        assert len(self.file.by_type("IfcRelAssignsToResource")) == 1
+        assert rel2.RelatedObjects == (actor,)