diff --git a/imperative/python/megengine/functional/elemwise.py b/imperative/python/megengine/functional/elemwise.py
index c1f1fff6390cceb245551f72aa4ab41cc9fc1c84..4a8c4d7b79e4d32899f04b190b4f8cae3013a228 100644
--- a/imperative/python/megengine/functional/elemwise.py
+++ b/imperative/python/megengine/functional/elemwise.py
@@ -16,7 +16,6 @@ from ..core.tensor import utils
 from ..core.tensor.array_method import _elwise_apply
 from ..core.tensor.utils import astype
 from ..device import get_default_device
-from ..jit.tracing import is_tracing
 from ..tensor import Tensor
 from ..utils.deprecation import deprecated_func
 
@@ -560,8 +559,8 @@ def clip(x: Tensor, lower=None, upper=None) -> Tensor:
     ), "At least one of 'lower' or 'upper' must not be None"
     if lower is not None:
         if upper is not None:
-            if not is_tracing():
-                assert lower <= upper, "clip lower bound is bigger that upper bound"
+            # FIXME: following assertion won't work during trace if upper and lower are Tensors
+            # assert lower <= upper, "clip lower bound is bigger that upper bound"
             return minimum(maximum(x, lower), upper)
         else:
             return maximum(x, lower)
diff --git a/imperative/python/megengine/functional/vision.py b/imperative/python/megengine/functional/vision.py
index cb9b339311a489bd89c2d2e0f6437bb076955b56..5e3bcfb1f197c7b2dc368b71eab3248e8d87e40b 100644
--- a/imperative/python/megengine/functional/vision.py
+++ b/imperative/python/megengine/functional/vision.py
@@ -12,7 +12,6 @@ from ..core._imperative_rt.core2 import apply
 from ..core.ops import builtin
 from ..core.tensor import megbrain_graph, utils
 from ..core.tensor.utils import astensor1d
-from ..jit.tracing import is_tracing
 from ..tensor import Tensor
 from .elemwise import floor
 from .math import argsort
@@ -226,6 +225,10 @@ def nms(
         otherwise it required to be specified; if it is not specified, all boxes are kept.
     :return: indices of the elements that have been kept by NMS, sorted by scores.
 
+    .. note::
+
+        max_output should be specified and should have valid positive value under tracing
+
     Examples:
 
     .. testcode::
@@ -263,11 +266,6 @@ def nms(
     sorted_idx = argsort(scores, descending=True)
     boxes = boxes[sorted_idx]
 
-    if is_tracing():
-        assert (
-            max_output is not None and max_output > 0
-        ), "max_output should be specified under tracing"
-
     if max_output is None:
         max_output = boxes.shape[0]