diff --git a/src/main/java/models/deltaAlgebra/DeltaComplex.java b/src/main/java/models/deltaAlgebra/DeltaComplex.java
index 34c579d..99a5bcf 100644
--- a/src/main/java/models/deltaAlgebra/DeltaComplex.java
+++ b/src/main/java/models/deltaAlgebra/DeltaComplex.java
@@ -130,10 +130,12 @@
 			}
 		}
 		List<Integer> lis = new ArrayList<>();
-		for (i = tails[len - 1]; i >= 0; i = prev[i]) {
-			lis.add(anotherPositions.get(i));
+		if (len > 0) {
+			for (i = tails[len - 1]; i >= 0; i = prev[i]) {
+				lis.add(anotherPositions.get(i));
+			}
+			Collections.reverse(lis);
 		}
-		Collections.reverse(lis);
 
 		DeltaComplex deltaComplex = null;
 		int anotherPrevPos = -1;