diff --git a/tools/pnnx/tests/ncnn/test_nn_Linear.py b/tools/pnnx/tests/ncnn/test_nn_Linear.py
index f074154c9..44b50b064 100644
--- a/tools/pnnx/tests/ncnn/test_nn_Linear.py
+++ b/tools/pnnx/tests/ncnn/test_nn_Linear.py
@@ -14,7 +14,10 @@ class Model(nn.Module):
         self.linear_1 = nn.Linear(in_features=16, out_features=13, bias=True)
 
         self.linear_2 = nn.Linear(in_features=13, out_features=17, bias=True)
-        if version.parse(torch.__version__) < version.parse('2.1'):
+        if version.parse(torch.__version__) < version.parse('1.9'):
+            # weight_norm on torch 1.8 produces wrong output shape, skip it
+            pass
+        elif version.parse(torch.__version__) < version.parse('2.1'):
             self.linear_2 = torch.nn.utils.weight_norm(self.linear_2)
         else:
             self.linear_2 = torch.nn.utils.parametrizations.weight_norm(self.linear_2)