diff --git a/brainpy/_src/math/random.py b/brainpy/_src/math/random.py
index 74190cb2..3f3a8446 100644
--- a/brainpy/_src/math/random.py
+++ b/brainpy/_src/math/random.py
@@ -67,10 +67,9 @@ def _size2shape(size):
 
 
 def _check_shape(name, shape, *param_shapes):
-  shape = core.as_named_shape(shape)
   if param_shapes:
-    shape_ = lax.broadcast_shapes(shape.positional, *param_shapes)
-    if shape.positional != shape_:
+    shape_ = lax.broadcast_shapes(shape, *param_shapes)
+    if shape != shape_:
       msg = ("{} parameter shapes must be broadcast-compatible with shape "
              "argument, and the result of broadcasting the shapes must equal "
              "the shape argument, but got result {} for shape argument {}.")