diff --git a/questionsService/question-model.js b/questionsService/question-model.js
index d077fcaa..fb088967 100644
--- a/questionsService/question-model.js
+++ b/questionsService/question-model.js
@@ -7,7 +7,7 @@ mongoose.connect('mongodb://mongodb:27017/questionsdb', { useNewUrlParser: true,
 
 //preguntas
 const preguntaSchema = new mongoose.Schema({
-    
+    _id: mongoose.Schema.Types.ObjectId,    
     textoPregunta: {
         type: String,
         required: true
@@ -26,7 +26,7 @@ const Pregunta = mongoose.model('Pregunta', preguntaSchema);
 
 //categoria
 const categoriaSchema = new mongoose.Schema({
-  
+  _id: mongoose.Schema.Types.ObjectId,
   nombre: {
     type: String,
     required: true
@@ -37,7 +37,7 @@ const Categoria = mongoose.model('Categoria', categoriaSchema);
 
 //Respuesta
 const respuestaSchema = new mongoose.Schema({
-  
+  _id: mongoose.Schema.Types.ObjectId,
   textoRespuesta: {
     type: String,
     required: true
@@ -51,7 +51,7 @@ const Respuesta = mongoose.model('Respuesta', respuestaSchema);
 
 //Tipos
 const tiposSchema = new mongoose.Schema({
-  
+  _id: mongoose.Schema.Types.ObjectId,
   idPreguntas: [{
     type: String,
     required: true