diff --git a/src/eva2/server/go/strategies/DynamicParticleSwarmOptimization.java b/src/eva2/server/go/strategies/DynamicParticleSwarmOptimization.java
index 40d6e301..6391efdf 100644
--- a/src/eva2/server/go/strategies/DynamicParticleSwarmOptimization.java
+++ b/src/eva2/server/go/strategies/DynamicParticleSwarmOptimization.java
@@ -402,7 +402,7 @@ public class DynamicParticleSwarmOptimization extends ParticleSwarmOptimization
 				break;
 				}
 			} else {
-				System.err.println("Could not perform PSO update, because individual is not instance of InterfaceESIndividual!");
+				throw new RuntimeException("Could not perform PSO update, because individual is not instance of InterfaceESIndividual!");
 			}
 		}
 		//if (AbstractEAIndividual.getDoublePosition(indy)[0]<500000) {
diff --git a/src/eva2/server/go/strategies/ParticleSwarmOptimization.java b/src/eva2/server/go/strategies/ParticleSwarmOptimization.java
index b97100fd..44b4ed99 100644
--- a/src/eva2/server/go/strategies/ParticleSwarmOptimization.java
+++ b/src/eva2/server/go/strategies/ParticleSwarmOptimization.java
@@ -600,7 +600,7 @@ public class ParticleSwarmOptimization implements InterfaceOptimizer, java.io.Se
 			default: System.err.println("particle type " + type + " unknown!"); break;
 			}
 		} else {
-			EVAERROR.errorMsgOnce("Could not perform PSO update, because individual is not instance of InterfaceESIndividual!");
+			throw new RuntimeException("Could not perform PSO update, because individual is not instance of InterfaceESIndividual!");
 		}
 	}