diff --git a/prism/src/prism/ExplicitFiles2MTBDD.java b/prism/src/prism/ExplicitFiles2MTBDD.java
index 8d8e290f..fa8779c1 100644
--- a/prism/src/prism/ExplicitFiles2MTBDD.java
+++ b/prism/src/prism/ExplicitFiles2MTBDD.java
@@ -673,7 +673,7 @@ public class ExplicitFiles2MTBDD
 		}
 		// Otherwise, construct from the labels
 		else {
-			start = labelsDD.get("init");
+			start = labelsDD.get("init").copy();
 			if (start == null || start.equals(JDD.ZERO)) {
 				throw new PrismException("No initial states found in labels file");
 			}