diff --git a/unsloth/models/_utils.py b/unsloth/models/_utils.py
index 116352c504..d6255d8ed9 100644
--- a/unsloth/models/_utils.py
+++ b/unsloth/models/_utils.py
@@ -242,8 +242,12 @@ def prefer_flex_attn_if_supported(model_class, config):
         # decode q_len=1, causing ValueError. Needs transformers update.
         # Gemma3N: timm vision wrappers (eg Gemma3nVisionConfig) do not
         # support flex_attention.
+        # NemotronH: hybrid Mamba-2 + Transformer model that does not
+        # support flex_attention (raises NotImplementedError from transformers).
         model_type = getattr(config, "model_type", "") if config else ""
-        if model_type in ("gpt_oss", "mllama") or str(model_type).startswith("gemma3n"):
+        if model_type in ("gpt_oss", "mllama", "nemotron_h") or str(
+            model_type
+        ).startswith("gemma3n"):
             return None
         if config is not None:
             setattr(config, "_attn_implementation", "flex_attention")