diff --git a/HeuristicLab.Tests/HeuristicLab-3.3/Samples/SamplesUtils.cs b/HeuristicLab.Tests/HeuristicLab-3.3/Samples/SamplesUtils.cs
index b511bbbcd8..6099fba9ab 100644
--- a/HeuristicLab.Tests/HeuristicLab-3.3/Samples/SamplesUtils.cs
+++ b/HeuristicLab.Tests/HeuristicLab-3.3/Samples/SamplesUtils.cs
@@ -20,7 +20,7 @@ public static void RunAlgorithm(IAlgorithm a) {
       a.ExceptionOccurred += (sender, e) => { ex = e.Value; };
       a.Prepare();
       a.Start();
-      Assert.IsNull(ex, ex.ToString());
+      Assert.IsNull(ex, ex?.ToString());
     }
 
     public static double GetDoubleResult(IAlgorithm a, string resultName) {