diff --git a/python/jittor/__init__.py b/python/jittor/__init__.py
index 157895bd..8127b138 100644
--- a/python/jittor/__init__.py
+++ b/python/jittor/__init__.py
@@ -273,6 +273,7 @@ Var.start_grad = Var.detach_inplace = detach_inplace
 
 def unsqueeze(x, dim):
     shape = list(x.shape)
+    if dim < 0: dim += len(shape)
     assert dim <= len(shape)
     return x.reshape(shape[:dim] + [1] + shape[dim:])
 Var.unsqueeze = unsqueeze