diff --git a/pyhf/tensor/mxnet_backend.py b/pyhf/tensor/mxnet_backend.py
index 398ba7bee1..0b0d55cdcf 100644
--- a/pyhf/tensor/mxnet_backend.py
+++ b/pyhf/tensor/mxnet_backend.py
@@ -39,9 +39,9 @@ def outer(self, tensor_in_1, tensor_in_2):
         tensor_1_shape = tensor_in_1.shape
         tensor_2_shape = tensor_in_2.shape
         if len(tensor_1_shape) == 1:
-            tensor_1_shape = (*tensor_1_shape, 1)
+            tensor_1_shape = (tensor_1_shape[0], 1)
         if len(tensor_2_shape) == 1:
-            tensor_2_shape = (*tensor_2_shape, 1)
+            tensor_2_shape = (tensor_2_shape[0], 1)
 
         rows1, cols1 = tensor_1_shape
         rows2, cols2 = tensor_2_shape