diff --git a/src/main/java/org/gridsuite/modification/modifications/byfilter/AbstractModificationByAssignment.java b/src/main/java/org/gridsuite/modification/modifications/byfilter/AbstractModificationByAssignment.java
index 3d4013cb..dcc9d567 100644
--- a/src/main/java/org/gridsuite/modification/modifications/byfilter/AbstractModificationByAssignment.java
+++ b/src/main/java/org/gridsuite/modification/modifications/byfilter/AbstractModificationByAssignment.java
@@ -56,8 +56,7 @@ public abstract class AbstractModificationByAssignment extends AbstractModificat
     public static final String VALUE_KEY_ARROW_NAME = "arrow";
     public static final String VALUE_KEY_ARROW_VALUE = "→";
     public static final String REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_ZERO = "network.modification.equipmentModifiedError.zero";
-    public static final String REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_EMPTY = "network.modification.equipmentModifiedError.empty";
-    public static final String REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_NAN = "network.modification.equipmentModifiedError.nan";
+    public static final String REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_MISSING = "network.modification.equipmentModifiedError.missing";
     public static final String REPORT_KEY_BY_FILTER_MODIFICATION_SOME = "network.modification.byFilterModificationSome";
     public static final String REPORT_KEY_BY_FILTER_MODIFICATION_FAILED = "network.modification.byFilterModificationFailed";
     public static final String REPORT_KEY_BY_FILTER_MODIFICATION_SUCCESS = "network.modification.byFilterModificationSuccess";
diff --git a/src/main/java/org/gridsuite/modification/modifications/byfilter/ByFormulaModification.java b/src/main/java/org/gridsuite/modification/modifications/byfilter/ByFormulaModification.java
index 57ed5b5b..1a054a60 100644
--- a/src/main/java/org/gridsuite/modification/modifications/byfilter/ByFormulaModification.java
+++ b/src/main/java/org/gridsuite/modification/modifications/byfilter/ByFormulaModification.java
@@ -68,12 +68,9 @@ protected boolean preCheckValue(Identifiable<?> equipment, AbstractAssignmentInf
         FormulaInfos formulaInfos = (FormulaInfos) abstractAssignmentInfos;
         Double value1 = formulaInfos.getFieldOrValue1().getRefOrValue(equipment);
         Double value2 = formulaInfos.getFieldOrValue2().getRefOrValue(equipment);
-        if (value1 == null || value2 == null) {
-            return reportErrorOnEquipment(equipment, notEditableEquipments, REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_EMPTY, reports);
-        }
-
+        // value 1 and value 2 cannot be null because getRefOrValue returns NaN if value is null
         if (Double.isNaN(value1) || Double.isNaN(value2)) {
-            return reportErrorOnEquipment(equipment, notEditableEquipments, REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_NAN, reports);
+            return reportErrorOnEquipment(equipment, notEditableEquipments, REPORT_KEY_EQUIPMENT_MODIFIED_ERROR_MISSING, reports);
         }
 
         if (value2 == 0 && formulaInfos.getOperator() == Operator.DIVISION) {
@@ -89,7 +86,7 @@ private boolean reportErrorOnEquipment(Identifiable<?> equipment, List<String> n
                 .withResourceBundles(NetworkModificationReportResourceBundle.BASE_NAME)
                 .withMessageTemplate(reportKey)
                 .withUntypedValue(VALUE_KEY_EQUIPMENT_NAME, equipment.getId())
-                .withSeverity(TypedValue.DETAIL_SEVERITY)
+                .withSeverity(TypedValue.WARN_SEVERITY)
                 .build());
         return false;
     }
diff --git a/src/main/resources/org/gridsuite/modification/reports.properties b/src/main/resources/org/gridsuite/modification/reports.properties
index 845a8db5..fce38641 100644
--- a/src/main/resources/org/gridsuite/modification/reports.properties
+++ b/src/main/resources/org/gridsuite/modification/reports.properties
@@ -145,8 +145,7 @@ network.modification.equipmentDeletion = Equipment deletion ${equipmentId}
 network.modification.equipmentDisconnect = Equipment with id=${id} disconnected
 network.modification.equipmentDisconnect.side = Equipment with id=${id} disconnected on side ${side}
 network.modification.equipmentDisconnected = Equipment with id=${id} disconnected
-network.modification.equipmentModifiedError.empty = Cannot modify equipment ${equipmentName} : At least one of the value or referenced field is empty
-network.modification.equipmentModifiedError.nan = Cannot modify equipment ${equipmentName} : At least one of the value or referenced field is not a number
+network.modification.equipmentModifiedError.missing = Cannot modify equipment ${equipmentName} : At least one of the value or referenced field is missing
 network.modification.equipmentModifiedError.zero = Cannot modify equipment ${equipmentName} : The value or referenced field of the second operand in the division operator is zero
 network.modification.equipmentModifiedReport = ${equipmentType} id : ${equipmentName}, ${fieldName} : ${oldValue} ${arrow} ${newValue}
 network.modification.equipmentModifiedReportException = Cannot modify equipment ${equipmentName} : ${errorMessage}
diff --git a/src/test/java/org/gridsuite/modification/modifications/byfilter/formula/VoltageLevelByFormulaModificationTest.java b/src/test/java/org/gridsuite/modification/modifications/byfilter/formula/VoltageLevelByFormulaModificationTest.java
index a69c7bee..6dbeb0d9 100644
--- a/src/test/java/org/gridsuite/modification/modifications/byfilter/formula/VoltageLevelByFormulaModificationTest.java
+++ b/src/test/java/org/gridsuite/modification/modifications/byfilter/formula/VoltageLevelByFormulaModificationTest.java
@@ -252,7 +252,7 @@ protected void assertAfterNetworkModificationApplication() {
 
         // check logs
         List<String> allLogs = reportNode.getChildren().getFirst().getChildren().stream().flatMap(child -> child.getChildren().stream().map(ReportNode::getMessage)).toList();
-        assertTrue(allLogs.contains("Cannot modify equipment v7 : At least one of the value or referenced field is not a number"));
+        assertTrue(allLogs.contains("Cannot modify equipment v7 : At least one of the value or referenced field is missing"));
         assertTrue(allLogs.contains("Cannot modify equipment v8 : The value or referenced field of the second operand in the division operator is zero"));
 
     }