diff --git a/src/eva2/server/go/problems/AbstractProblemDouble.java b/src/eva2/server/go/problems/AbstractProblemDouble.java
index 290bdf72..7a1c07da 100644
--- a/src/eva2/server/go/problems/AbstractProblemDouble.java
+++ b/src/eva2/server/go/problems/AbstractProblemDouble.java
@@ -122,7 +122,7 @@ public abstract class AbstractProblemDouble extends AbstractOptimizationProblem
         // set the fitness
         setEvalFitness(individual, x, fitness);
         if (isWithConstraints()) {
-        	individual.putData(rawFitKey, individual.getFitness());
+        	individual.putData(rawFitKey, individual.getFitness().clone());
         	addConstraints(individual, x);
         }
 	}