From 63462697992fd8ebd608ba617c811d9b3d703a91 Mon Sep 17 00:00:00 2001
From: Anas Khan <anasalimkhan@gmail.com>
Date: Mon, 8 Jan 2018 11:33:09 +0530
Subject: BUG: arrays not being flattened in `union1d`

---
 numpy/ma/extras.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'numpy/ma/extras.py')

diff --git a/numpy/ma/extras.py b/numpy/ma/extras.py
index 360d50d8a..cbf26cfb3 100644
--- a/numpy/ma/extras.py
+++ b/numpy/ma/extras.py
@@ -1209,7 +1209,7 @@ def union1d(ar1, ar2):
     numpy.union1d : Equivalent function for ndarrays.
 
     """
-    return unique(ma.concatenate((ar1, ar2)))
+    return unique(ma.concatenate((ar1.flatten(), ar2.flatten())))
 
 
 def setdiff1d(ar1, ar2, assume_unique=False):
-- 
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