diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
index ac04c80e7..994e4a943 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
@@ -147,7 +147,7 @@ public class Worker extends Resource implements Comparable {
         return !isVirtual();
     }
 
-    @AssertTrue(message = "Worker with the same nif previously existed")
+    @AssertTrue(message = "Worker ID already used. It has to be be unique")
     public boolean checkConstraintUniqueNif() {
         if (!areFirstNameSurnameNifSpecified()) {
             return true;
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/ReportAdvancesServiceREST.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/ReportAdvancesServiceREST.java
index d165a5c54..4a4877381 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/ReportAdvancesServiceREST.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/ReportAdvancesServiceREST.java
@@ -97,7 +97,7 @@ public class ReportAdvancesServiceREST implements IReportAdvancesService {
 
         if (StringUtils
                 .isEmpty(orderElementWithAdvanceMeasurementsListDTO.externalCompanyNif)) {
-            return getErrorMessage("", "external company nif not specified");
+            return getErrorMessage("", "external company ID not specified");
         }
 
         ExternalCompany externalCompany;
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
index 8f66d6e54..c73acc12a 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/ws/subcontract/impl/SubcontractServiceREST.java
@@ -133,7 +133,7 @@ public class SubcontractServiceREST implements ISubcontractService {
 
         if (StringUtils.isEmpty(subcontractedTask.externalCompanyNif)) {
             throw new ViolationError(subcontractedTask.subcontractedCode,
-                    "external company nif not specified");
+                    "external company ID not specified");
         }
 
         final ExternalCompany externalCompany = adHocTransactionService
diff --git a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
index 614e7d70c..8b9886ba3 100644
--- a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
+++ b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
@@ -193,7 +193,7 @@ public class ResourceServiceTest {
         saveResource(w1);
 
         /*
-         * Create a worker DTO with the same first name, surname, and nif as
+         * Create a worker DTO with the same first name, surname, and ID as
          * the previous one.
          */
         WorkerDTO w2 = new WorkerDTO(w1.getFirstName(), w1.getSurname(),