diff --git a/skimage/graph/tests/test_rag.py b/skimage/graph/tests/test_rag.py
index 35eb5c38..0d5fa2ab 100644
--- a/skimage/graph/tests/test_rag.py
+++ b/skimage/graph/tests/test_rag.py
@@ -100,7 +100,6 @@ def test_cut_normalized():
     assert new_labels.max() == 1
 
 
-@skipif(not is_installed('networkx'))
 def test_rag_error():
     img = np.zeros((10, 10, 3), dtype='uint8')
     labels = np.zeros((10, 10), dtype='uint8')
@@ -108,3 +107,23 @@ def test_rag_error():
     labels[5:, :] = 1
     testing.assert_raises(ValueError, graph.rag_mean_color, img, labels,
                           2, 'non existant mode')
+
+@skipif(not is_installed('networkx'))
+def test_merge_hierarchical():
+    img = np.zeros((100, 100, 3), dtype='uint8')
+    img[:50, :50] = 255, 255, 255
+    img[:50, 50:] = 254, 254, 254
+    img[50:, :50] = 2, 2, 2
+    img[50:, 50:] = 1, 1, 1
+
+    labels = np.zeros((100, 100), dtype='uint8')
+    labels[:50, :50] = 0
+    labels[:50, 50:] = 1
+    labels[50:, :50] = 2
+    labels[50:, 50:] = 3
+
+    rag = graph.rag_mean_color(img, labels)
+    new_labels = graph.merge_hierarchical(labels, rag, 10)
+
+    # Two labels
+    assert new_labels.max() == 1