diff --git a/lib/src/modelos/Definic.dart b/lib/src/modelos/Definic.dart
index bd22c3f..3c9ac3d 100644
--- a/lib/src/modelos/Definic.dart
+++ b/lib/src/modelos/Definic.dart
@@ -40,7 +40,8 @@ abstract class Definic {
      * Al ser una clase abstracta, hay que crear un constructor propio:
      * https://github.com/dart-lang/json_serializable/issues/606#issuecomment-587993029
      */
-    factory Definic.fromJson(Map<String, dynamic> json) {
+    factory Definic.fromJson (Map<String, dynamic> json) {
+
 
         switch (json ["clase"]) {
 
@@ -55,8 +56,9 @@ abstract class Definic {
                 return Expr.fromJson (json);
 
             default:
-                throw ArgumentError ("Invalid value provided: ${json["clase"]}. "
-                                    " Should be one of ${ClaseAcepc.values}"
+                throw ArgumentError ("Invalid class value provided: ${json["clase"]}. "
+                                    "Should be one of ${ClaseAcepc.values}. "
+                                    "This JSON's keys are: ${json.keys}"
                 );
         }
     }
diff --git a/lib/src/modelos/Expr.dart b/lib/src/modelos/Expr.dart
index 4330ef7..cd5aac3 100644
--- a/lib/src/modelos/Expr.dart
+++ b/lib/src/modelos/Expr.dart
@@ -52,9 +52,12 @@ class Expr extends Definic {
     /**
      * Constructor por defecto.
      * Simplemente inicializa los atributos
+     *
+     * El parámetro "clase" se declara explícitamente para poder serializar correctamente
+     * (ver https://github.com/dart-lang/json_serializable/issues/274).
      */
     Expr (String this.texto
-        , { String id = null, List<Acepc> definiciones = null }
+        , { String id = null, List<Acepc> definiciones = null , ClaseAcepc clase}
     ):
         this.definiciones = (definiciones == null)? [] : definiciones
         , super (id, ClaseAcepc.frase_hecha)
diff --git a/lib/src/modelos/Expr.g.dart b/lib/src/modelos/Expr.g.dart
index c0edc98..9adab94 100644
--- a/lib/src/modelos/Expr.g.dart
+++ b/lib/src/modelos/Expr.g.dart
@@ -16,11 +16,53 @@ Expr _$ExprFromJson(Map<String, dynamic> json) {
                 e == null ? null : Acepc.fromJson(e as Map<String, dynamic>))
             ?.toList() ??
         [],
+    clase: _$enumDecodeNullable(_$ClaseAcepcEnumMap, json['clase']) ??
+        ClaseAcepc.manual,
   );
 }
 
 Map<String, dynamic> _$ExprToJson(Expr instance) => <String, dynamic>{
       'id': instance.id,
+      'clase': _$ClaseAcepcEnumMap[instance.clase],
       'texto': instance.texto,
       'definiciones': instance.definiciones?.map((e) => e?.toJson())?.toList(),
     };
+
+T _$enumDecode<T>(
+  Map<T, dynamic> enumValues,
+  dynamic source, {
+  T unknownValue,
+}) {
+  if (source == null) {
+    throw ArgumentError('A value must be provided. Supported values: '
+        '${enumValues.values.join(', ')}');
+  }
+
+  final value = enumValues.entries
+      .singleWhere((e) => e.value == source, orElse: () => null)
+      ?.key;
+
+  if (value == null && unknownValue == null) {
+    throw ArgumentError('`$source` is not one of the supported values: '
+        '${enumValues.values.join(', ')}');
+  }
+  return value ?? unknownValue;
+}
+
+T _$enumDecodeNullable<T>(
+  Map<T, dynamic> enumValues,
+  dynamic source, {
+  T unknownValue,
+}) {
+  if (source == null) {
+    return null;
+  }
+  return _$enumDecode<T>(enumValues, source, unknownValue: unknownValue);
+}
+
+const _$ClaseAcepcEnumMap = {
+  ClaseAcepc.manual: 'manual',
+  ClaseAcepc.normal: 'normal',
+  ClaseAcepc.frase_hecha: 'frase_hecha',
+  ClaseAcepc.enlace: 'enlace',
+};