diff --git a/imperative/python/megengine/quantization/utils.py b/imperative/python/megengine/quantization/utils.py
index 2cd1eecb38818a9a6dbc6e15d3181c26899da46f..00699d3fba3de85d414bc80fae23dd759d53fc76 100644
--- a/imperative/python/megengine/quantization/utils.py
+++ b/imperative/python/megengine/quantization/utils.py
@@ -206,20 +206,26 @@ def fake_quant_bias(bias: Tensor, inp: Tensor, w_qat: Tensor) -> Tensor:
     ):
         inp_params = inp.qparams
         w_params = w_qat.qparams
-        if inp_params.scale is not None and w_params.scale is not None:
-            assert inp_params.mode == w_params.mode, "incompatible QuantMode"
-            # TODO: support quint8 dtype.
-            assert (
-                inp_params.dtype_meta.np_dtype_str == "int8"
-                and w_params.dtype_meta.np_dtype_str == "int8"
-            ), "fake_quant_bias only support int8 like dtype now"
-
-            # use the same mode with weight.
-            # TODO: avoid hardcode
-            b_dtype = _builtin_quant_dtypes["qint32"]
-            b_param = create_qparams(
-                w_params.mode, b_dtype, scale=inp_params.scale * w_params.scale
-            )
-            b_qat = fake_quant_tensor(bias, b_param)
-            b_qat.qparams.update(b_param)
+
+        if inp_params.scale is None or w_params.scale is None:
+            return b_qat
+
+        # TODO: support different mode
+        if inp_params.mode != w_params.mode:
+            return b_qat
+
+        # TODO: support quint8 dtype.
+        if inp_params.dtype_meta.np_dtype_str != "int8":
+            return b_qat
+        if w_params.dtype_meta.np_dtype_str != "int8":
+            return b_qat
+
+        # use the same mode with weight.
+        # TODO: avoid hardcode
+        b_dtype = _builtin_quant_dtypes["qint32"]
+        b_param = create_qparams(
+            w_params.mode, b_dtype, scale=inp_params.scale * w_params.scale
+        )
+        b_qat = fake_quant_tensor(bias, b_param)
+        b_qat.qparams.update(b_param)
     return b_qat