diff --git a/src/main/java/fr/inra/oresing/checker/ReferenceLineChecker.java b/src/main/java/fr/inra/oresing/checker/ReferenceLineChecker.java
index 0daaefac4e5dcf43c63fd747d50d13e2353e6f25..457158f3aa17ac523b308e217902fb17dc108bdb 100644
--- a/src/main/java/fr/inra/oresing/checker/ReferenceLineChecker.java
+++ b/src/main/java/fr/inra/oresing/checker/ReferenceLineChecker.java
@@ -7,7 +7,9 @@ import fr.inra.oresing.persistence.SqlPrimitiveType;
 import fr.inra.oresing.rest.validationcheckresults.ReferenceValidationCheckResult;
 import fr.inra.oresing.transformer.LineTransformer;
 
+import java.util.HashSet;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 public class ReferenceLineChecker implements CheckerOnOneVariableComponentLineChecker<ReferenceLineCheckerConfiguration> {
 
@@ -47,8 +49,8 @@ public class ReferenceLineChecker implements CheckerOnOneVariableComponentLineCh
             validationCheckResult = ReferenceValidationCheckResult.success(target, rawValue, valueAsLtree, referenceValues.get(valueAsLtree));
         } else {
             validationCheckResult = ReferenceValidationCheckResult.error(target, rawValue, getTarget().getInternationalizedKey("invalidReference"), ImmutableMap.of(
-                    "target", target,
-                    "referenceValues", referenceValues,
+                    "target", target.toHumanReadableString(),
+                    "referenceValues", referenceValues==null?new HashSet<>():referenceValues.keySet().stream().map(Ltree::getSql).collect(Collectors.toSet()),
                     "refType", reference,
                     "value", rawValue));
         }
@@ -73,4 +75,4 @@ public class ReferenceLineChecker implements CheckerOnOneVariableComponentLineCh
     public SqlPrimitiveType getSqlType() {
         return SqlPrimitiveType.LTREE;
     }
-}
+}
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