diff --git a/critdd/diagram.py b/critdd/diagram.py
index 640188a..5d506f2 100644
--- a/critdd/diagram.py
+++ b/critdd/diagram.py
@@ -109,6 +109,7 @@ def get_groups(self, alpha=.05, adjustment="holm", return_names=False, return_si
                 np.logical_or(r_min >= r_min[i], r_max < r_max[i])
             ))
         groups = [ g for (g, i) in zip(groups, is_maximal) if i ] # remove non-maximal groups
+        groups = [ np.array(g) for g in set(tuple(g) for g in groups) ] # remove duplicates
         if not return_singletons:
             groups = list(filter(lambda g: len(g) > 1, groups))
         if return_names:
diff --git a/setup.py b/setup.py
index 126b1f6..285475f 100644
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,7 @@ def readme():
 
 setup(
     name="critdd",
-    version="0.0.4-dev",
+    version="0.0.4",
     description="Critical difference diagrams with Python and Tikz",
     long_description=readme(),
     classifiers=[