diff --git a/prism/src/prism/Result.java b/prism/src/prism/Result.java
index e68a4ba2..93c1b548 100644
--- a/prism/src/prism/Result.java
+++ b/prism/src/prism/Result.java
@@ -129,6 +129,6 @@ public class Result
 	 */
 	public String toString()
 	{
-		return result.toString();
+		return result == null ? "null" : result.toString();
 	}
 }