diff --git a/dynawaltz/src/main/java/com/powsybl/dynawaltz/builders/ModelConfigs.java b/dynawaltz/src/main/java/com/powsybl/dynawaltz/builders/ModelConfigs.java
index 394f2dab4..ba0b3e1af 100644
--- a/dynawaltz/src/main/java/com/powsybl/dynawaltz/builders/ModelConfigs.java
+++ b/dynawaltz/src/main/java/com/powsybl/dynawaltz/builders/ModelConfigs.java
@@ -48,7 +48,7 @@ public Set<ModelInfo> getModelInfos() {
     }
 
     Set<String> getModelsName() {
-        return modelConfigMap.keySet();
+        return Set.copyOf(modelConfigMap.keySet());
     }
 
     void addModelConfigs(ModelConfigs modelConfigsToMerge) {