diff --git a/holoviews/core/data/dictionary.py b/holoviews/core/data/dictionary.py
index 28cc115b0a..f965e204c1 100644
--- a/holoviews/core/data/dictionary.py
+++ b/holoviews/core/data/dictionary.py
@@ -217,7 +217,7 @@ def values(cls, dataset, dim, expanded=True, flat=True):
         else:
             if not expanded:
                 return util.unique_array(values)
-            values = np.array(values)
+            values = np.asarray(values)
         return values
 
 
diff --git a/holoviews/core/util.py b/holoviews/core/util.py
index b539d15497..973689c7e2 100644
--- a/holoviews/core/util.py
+++ b/holoviews/core/util.py
@@ -838,7 +838,10 @@ def unique_array(arr):
     if not len(arr):
         return arr
     elif pd:
-        return pd.unique(arr)
+        unique = pd.unique(arr)
+        if isinstance(arr, np.ndarray) and unique.dtype != arr.dtype:
+            return unique.astype(arr.dtype)
+        return unique
     else:
         arr = np.asarray(arr)
         _, uniq_inds = np.unique(arr, return_index=True)
diff --git a/holoviews/plotting/bokeh/graphs.py b/holoviews/plotting/bokeh/graphs.py
index f340666f61..3803ef565a 100644
--- a/holoviews/plotting/bokeh/graphs.py
+++ b/holoviews/plotting/bokeh/graphs.py
@@ -93,6 +93,7 @@ def _get_edge_colors(self, element, ranges, edge_data, edge_mapping, style):
         field = dimension_sanitizer(cdim.name)
         cvals = element.dimension_values(cdim)
         if idx in self._node_columns:
+            print(element.nodes.interface)
             factors = element.nodes.dimension_values(2, expanded=False)
         elif idx == 2 and cvals.dtype.kind in 'if':
             factors = None
diff --git a/tests/testbokehgraphs.py b/tests/testbokehgraphs.py
index 7a2ed25a5d..00ff9ca0b3 100644
--- a/tests/testbokehgraphs.py
+++ b/tests/testbokehgraphs.py
@@ -34,7 +34,7 @@ def setUp(self):
         self.weights = np.random.rand(N)
         self.graph = Graph(((self.source, self.target),))
         self.node_info = Dataset(['Output']+['Input']*(N-1), vdims=['Label'])
-        self.node_info2 = Dataset(self.weights, vdims='Weight')
+        self.node_info2 = Dataset(self.weights, vdims='Weight', datatype=['dictionary'])
         self.graph2 = Graph(((self.source, self.target), self.node_info))
         self.graph3 = Graph(((self.source, self.target), self.node_info2), datatype=['dictionary'])
         self.graph4 = Graph(((self.source, self.target, self.weights),), vdims='Weight')