diff --git a/tests/functional/test_metrics.py b/tests/functional/test_metrics.py
index 4dbefd34603..6cf33a3eaa4 100644
--- a/tests/functional/test_metrics.py
+++ b/tests/functional/test_metrics.py
@@ -319,9 +319,20 @@ def test_schema_no_metrics(service, namespace):
         my_metrics.serialize_metric_set()
 
 
-def test_exceed_number_of_dimensions(metric, namespace, monkeypatch):
-    # GIVEN we we have more dimensions than CloudWatch supports
-    # and that service dimension is injected like a user-defined dimension (N+1)
+def test_exceed_number_of_dimensions(metric, namespace):
+    # GIVEN we have more dimensions than CloudWatch supports
+    dimensions = [{"name": f"test_{i}", "value": "test"} for i in range(11)]
+
+    # WHEN we attempt to serialize them into a valid EMF object
+    # THEN it should fail validation and raise SchemaValidationError
+    with pytest.raises(SchemaValidationError, match="Maximum number of dimensions exceeded.*"):
+        with single_metric(**metric, namespace=namespace) as my_metric:
+            for dimension in dimensions:
+                my_metric.add_dimension(**dimension)
+
+
+def test_exceed_number_of_dimensions_with_service(metric, namespace, monkeypatch):
+    # GIVEN we have service set and add more dimensions than CloudWatch supports (N+1)
     monkeypatch.setenv("POWERTOOLS_SERVICE_NAME", "test_service")
     dimensions = [{"name": f"test_{i}", "value": "test"} for i in range(9)]