diff --git a/tests/cupy_tests/manipulation_tests/test_join.py b/tests/cupy_tests/manipulation_tests/test_join.py
index e03a121d595..590721d1a01 100644
--- a/tests/cupy_tests/manipulation_tests/test_join.py
+++ b/tests/cupy_tests/manipulation_tests/test_join.py
@@ -108,12 +108,16 @@ def test_concatenate_many_multi_dptye(self, xp):
         b = testing.shaped_arange((2, 1), xp, 'f')
         return xp.concatenate((a, b) * 1024, axis=1)
 
-    @testing.numpy_cupy_array_equal()
     @testing.slow
-    def test_concatenate_32bit_boundary(self, xp):
-        a = xp.zeros((2 ** 30,), dtype=xp.int8)
-        b = xp.zeros((2 ** 30,), dtype=xp.int8)
-        return xp.concatenate([a, b])
+    def test_concatenate_32bit_boundary(self):
+        a = cupy.zeros((2 ** 30,), dtype=cupy.int8)
+        b = cupy.zeros((2 ** 30,), dtype=cupy.int8)
+        ret = cupy.concatenate([a, b])
+        del a
+        del b
+        del ret
+        # Free huge memory for slow test
+        cupy.get_default_memory_pool().free_all_blocks()
 
     def test_concatenate_wrong_ndim(self):
         a = cupy.empty((2, 3))