diff --git a/src/llamafactory/data/converter.py b/src/llamafactory/data/converter.py
index ad49deded4..cdd7308549 100644
--- a/src/llamafactory/data/converter.py
+++ b/src/llamafactory/data/converter.py
@@ -198,19 +198,19 @@ def __call__(self, example: dict[str, Any]) -> dict[str, Any]:
                 or rejected[self.dataset_attr.role_tag] not in accept_tags[-1]
             ):
                 logger.warning_rank0(f"Invalid role tag in {[chosen, rejected]}.")
-                broken_data = True
-
-            prompt = aligned_messages
-            response = [
-                {
-                    "role": tag_mapping[chosen[self.dataset_attr.role_tag]],
-                    "content": chosen[self.dataset_attr.content_tag],
-                },
-                {
-                    "role": tag_mapping[rejected[self.dataset_attr.role_tag]],
-                    "content": rejected[self.dataset_attr.content_tag],
-                },
-            ]
+                prompt, response = [], []
+            else:
+                prompt = aligned_messages
+                response = [
+                    {
+                        "role": tag_mapping[chosen[self.dataset_attr.role_tag]],
+                        "content": chosen[self.dataset_attr.content_tag],
+                    },
+                    {
+                        "role": tag_mapping[rejected[self.dataset_attr.role_tag]],
+                        "content": rejected[self.dataset_attr.content_tag],
+                    },
+                ]
         else:  # normal example
             prompt = aligned_messages[:-1]
             response = aligned_messages[-1:]
@@ -275,6 +275,11 @@ def __call__(self, example: dict[str, Any]) -> dict[str, Any]:
                 )
                 tool_responses = []
 
+            if role not in tag_mapping:
+                logger.warning_rank0(f"Invalid role tag in {messages}.")
+                broken_data = True
+                break
+
             aligned_messages.append(
                 {
                     "role": tag_mapping[role],
@@ -319,19 +324,19 @@ def __call__(self, example: dict[str, Any]) -> dict[str, Any]:
                 or rejected[self.dataset_attr.role_tag] not in accept_tags[-1]
             ):
                 logger.warning_rank0(f"Invalid role tag in {[chosen, rejected]}.")
-                broken_data = True
-
-            prompt = aligned_messages
-            response = [
-                {
-                    "role": tag_mapping[chosen[self.dataset_attr.role_tag]],
-                    "content": chosen[self.dataset_attr.content_tag],
-                },
-                {
-                    "role": tag_mapping[rejected[self.dataset_attr.role_tag]],
-                    "content": rejected[self.dataset_attr.content_tag],
-                },
-            ]
+                prompt, response = [], []
+            else:
+                prompt = aligned_messages
+                response = [
+                    {
+                        "role": tag_mapping[chosen[self.dataset_attr.role_tag]],
+                        "content": chosen[self.dataset_attr.content_tag],
+                    },
+                    {
+                        "role": tag_mapping[rejected[self.dataset_attr.role_tag]],
+                        "content": rejected[self.dataset_attr.content_tag],
+                    },
+                ]
         else:  # normal example
             prompt = aligned_messages[:-1]
             response = aligned_messages[-1:]
diff --git a/tests/data/test_converter.py b/tests/data/test_converter.py
index 6b411aed53..ffb357efd0 100644
--- a/tests/data/test_converter.py
+++ b/tests/data/test_converter.py
@@ -62,3 +62,41 @@ def test_sharegpt_converter():
         "_videos": None,
         "_audios": None,
     }
+
+
+@pytest.mark.runs_on(["cpu", "mps"])
+def test_sharegpt_converter_ranking_skips_invalid_role():
+    # A pairwise (ranking) example whose chosen/rejected carries a role tag not
+    # in the accepted set must be skipped, not crash with KeyError on tag_mapping.
+    dataset_attr = DatasetAttr("hf_hub", "llamafactory/tiny-supervised-dataset")
+    dataset_attr.ranking = True
+    dataset_attr.chosen = "chosen"
+    dataset_attr.rejected = "rejected"
+    data_args = DataArguments()
+    example = {
+        "conversations": [{"from": "human", "value": "Solve the math problem.\n3 + 4"}],
+        "chosen": {"from": "not_a_role", "value": "The answer is 7."},
+        "rejected": {"from": "gpt", "value": "The answer is 8."},
+    }
+    dataset_converter = get_dataset_converter("sharegpt", dataset_attr, data_args)
+    result = dataset_converter(example)
+    assert result["_prompt"] == []
+    assert result["_response"] == []
+
+
+@pytest.mark.runs_on(["cpu", "mps"])
+def test_openai_converter_main_loop_skips_invalid_role():
+    # An openai-format message list containing a role tag not in tag_mapping must
+    # be skipped (prompt=[], response=[]), not crash with KeyError.
+    dataset_attr = DatasetAttr("hf_hub", "llamafactory/tiny-supervised-dataset")
+    data_args = DataArguments()
+    example = {
+        "conversations": [
+            {"from": "human", "value": "Solve the math problem.\n3 + 4"},
+            {"from": "not_a_role", "value": "The answer is 7."},
+        ]
+    }
+    dataset_converter = get_dataset_converter("openai", dataset_attr, data_args)
+    result = dataset_converter(example)
+    assert result["_prompt"] == []
+    assert result["_response"] == []