diff --git a/deconvolution/dgraph/VariableDGIndex.py b/deconvolution/dgraph/VariableDGIndex.py
index 013bb9964c5fe19e100075d4d618acde5b8e8dc3..535230ad3884285b24872bf6cdd7cac8ae4a365e 100644
--- a/deconvolution/dgraph/VariableDGIndex.py
+++ b/deconvolution/dgraph/VariableDGIndex.py
@@ -17,6 +17,6 @@ class VariableDGIndex(AbstractDGIndex):
     def add_dgraph(self, dg):
         barcodes = dg.node_set
 
-        for size in range(len(barcodes)-self.size, len(barcodes)+1):
+        for size in range(max(1, len(barcodes)-self.size), len(barcodes)+1):
             for tup in combinations(barcodes, size):
                 self.add_value(frozenset(tup), dg)