diff --git a/omegaconf/_utils.py b/omegaconf/_utils.py
index ffec246a3..978bfae99 100644
--- a/omegaconf/_utils.py
+++ b/omegaconf/_utils.py
@@ -137,6 +137,7 @@ def get_yaml_loader() -> Any:
     class OmegaConfLoader(yaml.SafeLoader):  # type: ignore
         def construct_mapping(self, node: yaml.Node, deep: bool = False) -> Any:
             keys = set()
+            constructor = super().construct_mapping(node, deep=deep)
             for key_node, value_node in node.value:
                 if key_node.tag != yaml.resolver.BaseResolver.DEFAULT_SCALAR_TAG:
                     continue
@@ -148,7 +149,7 @@ def construct_mapping(self, node: yaml.Node, deep: bool = False) -> Any:
                         key_node.start_mark,
                     )
                 keys.add(key_node.value)
-            return super().construct_mapping(node, deep=deep)
+            return constructor
 
     loader = OmegaConfLoader
     loader.add_implicit_resolver(
diff --git a/tests/test_create.py b/tests/test_create.py
index 66b073cd8..f8249c17d 100644
--- a/tests/test_create.py
+++ b/tests/test_create.py
@@ -424,12 +424,27 @@ def test_yaml_merge() -> None:
             c:
                 <<: *A
                 <<: *B
-                x: 3
+                w: 3
                 z: 1
             """
         )
     )
-    assert cfg == {"a": {"x": 1}, "b": {"y": 2}, "c": {"x": 3, "y": 2, "z": 1}}
+    assert cfg == {"a": {"x": 1}, "b": {"y": 2}, "c": {"x": 1, "y": 2, "w": 3, "z": 1}}
+
+
+def test_yaml_merge_with_conflict() -> None:
+    with raises(yaml.constructor.ConstructorError):
+        OmegaConf.create(
+            dedent(
+                """\
+                a: &A
+                    x: 1
+                c:
+                    <<: *A
+                    x: 3
+                """
+            )
+        )
 
 
 @mark.parametrize(