diff --git a/skimage/graph/tests/test_mcp.py b/skimage/graph/tests/test_mcp.py
index 1f62915262b..6bf8f97466d 100644
--- a/skimage/graph/tests/test_mcp.py
+++ b/skimage/graph/tests/test_mcp.py
@@ -11,10 +11,10 @@
 a[1:-1, 1] = 0
 a[1, 1:-1] = 0
 
+warning_optional = r'|\A\Z'
 
 def test_basic():
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(a, fully_connected=True)
     costs, traceback = m.find_costs([(1, 6)])
     return_path = m.traceback((7, 2))
@@ -56,15 +56,13 @@ def test_neg_inf():
                      (6, 1)]
     test_neg = np.where(a == 1, -1, 0)
     test_inf = np.where(a == 1, np.inf, 0)
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(test_neg, fully_connected=True)
     costs, traceback = m.find_costs([(1, 6)])
     return_path = m.traceback((6, 1))
     assert_array_equal(costs, expected_costs)
     assert_array_equal(return_path, expected_path)
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(test_inf, fully_connected=True)
     costs, traceback = m.find_costs([(1, 6)])
     return_path = m.traceback((6, 1))
@@ -73,8 +71,7 @@ def test_neg_inf():
 
 
 def test_route():
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         return_path, cost = mcp.route_through_array(a, (1, 6), (7, 2),
                                                     geometric=True)
     assert_almost_equal(cost, np.sqrt(2) / 2)
@@ -93,8 +90,7 @@ def test_route():
 
 
 def test_no_diagonal():
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(a, fully_connected=False)
     costs, traceback = m.find_costs([(1, 6)])
     return_path = m.traceback((7, 2))
@@ -125,8 +121,7 @@ def test_no_diagonal():
 
 def test_offsets():
     offsets = [(1, i) for i in range(10)] + [(1, -i) for i in range(1, 10)]
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(a, offsets=offsets)
     costs, traceback = m.find_costs([(1, 6)])
     assert_array_equal(traceback,
@@ -152,8 +147,7 @@ def _test_random(shape):
               (np.random.rand(len(shape)) * shape).astype(int)]
     ends = [(np.random.rand(len(shape)) * shape).astype(int)
             for i in range(4)]
-    optional = r'|\A\Z'
-    with expected_warnings(['Upgrading NumPy' + optional]):
+    with expected_warnings(['Upgrading NumPy' + warning_optional]):
         m = mcp.MCP(a, fully_connected=True)
     costs, offsets = m.find_costs(starts)
     for point in [(np.random.rand(len(shape)) * shape).astype(int)