diff --git a/package.json b/package.json
index 020ecf72..3ad8b23e 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "wollok-ts",
   "version": "4.0.4",
-  "wollokVersion": "3.1.7",
+  "wollokVersion": "3.1.8",
   "description": "TypeScript based Wollok language implementation",
   "repository": "https://github.com/uqbar-project/wollok-ts",
   "license": "MIT",
diff --git a/src/validator.ts b/src/validator.ts
index 2dcf71ec..f88451a0 100644
--- a/src/validator.ts
+++ b/src/validator.ts
@@ -161,7 +161,7 @@ export const shouldNotReassignConst = error<Assignment>(node => {
 })
 
 // TODO: Test if the reference points to the right kind of node
-export const missingReference = error<Reference<Node>>(node => !!node.target )
+export const missingReference = error<Reference<Node>>(node => !!node.target)
 
 export const shouldNotHaveLoopInHierarchy = error<Class | Mixin>(node => !allParents(node).includes(node))
 
@@ -218,11 +218,15 @@ export const shouldPassValuesToAllAttributes = error<New>(
   node => getUninitializedAttributesForInstantation(node),
 )
 
-export const shouldInitializeAllAttributes = error<Singleton>(
-  node => isEmpty(getUninitializedAttributes(node)),
-  node => getUninitializedAttributes(node)
+export const shouldInitializeInheritedAttributes = error<Singleton>(
+  node => isEmpty(getInheritedUninitializedAttributes(node)),
+  node => [getInheritedUninitializedAttributes(node).join(', ')],
 )
 
+export const shouldInitializeSingletonAttribute = error<Field>(node => {
+  return !node.parent.is(Singleton) || !isUninitialized(node.value)
+})
+
 export const shouldNotUseSelf = error<Self>(node => {
   const ancestors = node.ancestors
   return node.isSynthetic || !ancestors.some(is(Program)) || ancestors.some(is(Singleton))
@@ -395,7 +399,7 @@ export const shouldUseConditionalExpression = warning<If>(node => {
     elseValue === undefined ||
     ![true, false].includes(thenValue) ||
     thenValue === elseValue) && (!nextSentence ||
-    ![true, false].includes(valueFor(nextSentence))
+      ![true, false].includes(valueFor(nextSentence))
   )
 })
 
@@ -511,17 +515,27 @@ const getUninitializedAttributesForInstantation = (node: New): string[] => {
   const target = node.instantiated.target
   if (!target) return []
   const initializers = node.args.map(_ => _.name)
-  return getUninitializedAttributes(target, initializers)
+  return getAllUninitializedAttributes(target, initializers)
 }
 
-const getUninitializedAttributes = (node: Module, initializers: string[] = []) =>
-  node.allFields
-    .filter(field => {
+const getAllUninitializedAttributes = (node: Module, initializers: string[] = []) =>
+  getUninitializedAttributesIn(node, [...node.allFields], initializers)
+
+const getInheritedUninitializedAttributes = (node: Module, initializers: string[] = []) =>
+  getUninitializedAttributesIn(node, [...node.allFields.filter(f => f.parent !== node)], initializers)
+
+
+const getUninitializedAttributesIn = (node: Module, fields: Field[], initializers: string[] = []) =>
+  fields.
+    filter(field => {
       const value = node.defaultValueFor(field)
-      return value.isSynthetic && value.is(Literal) && value.isNull() && !initializers.includes(field.name)
+      return isUninitialized(value) && !initializers.includes(field.name)
     })
     .map(field => field.name)
 
+
+const isUninitialized = (value: Expression) => value.isSynthetic && value.is(Literal) && value.isNull()
+
 const isBooleanLiteral = (node: Expression, value: boolean) => node.is(Literal) && node.value === value
 
 const targetSupertypes = (node: Class | Singleton) => node.supertypes.map(_ => _?.reference.target)
@@ -560,10 +574,10 @@ const referencesSingleton = (node: Expression) => node.is(Reference) && node.tar
 
 const isBooleanOrUnknownType = (node: Node): boolean => match(node)(
   when(Literal)(condition => condition.value === true || condition.value === false),
-  when(Send)( _ =>  true), // tackled in a different validator
-  when(Super)( _ => true),
-  when(Reference)( condition => !condition.target?.is(Singleton)),
-  when(Node)( _ => false),
+  when(Send)(_ => true), // tackled in a different validator
+  when(Super)(_ => true),
+  when(Reference)(condition => !condition.target?.is(Singleton)),
+  when(Node)(_ => false),
 )
 
 const valueFor: any | undefined = (node: Node) =>
@@ -746,9 +760,9 @@ const validationsByKind = (node: Node): Record<string, Validation<any>> => match
   when(Program)(() => ({ nameShouldNotBeKeyword, shouldNotUseReservedWords, shouldMatchFileExtension, shouldNotDuplicateEntities })),
   when(Test)(() => ({ shouldHaveNonEmptyName, shouldNotMarkMoreThanOneOnlyTest, shouldHaveAssertInTest, shouldMatchFileExtension })),
   when(Class)(() => ({ nameShouldBeginWithUppercase, nameShouldNotBeKeyword, shouldNotHaveLoopInHierarchy, linearizationShouldNotRepeatNamedArguments, shouldNotDefineMoreThanOneSuperclass, superclassShouldBeLastInLinearization, shouldNotDuplicateGlobalDefinitions, shouldNotDuplicateVariablesInLinearization, shouldImplementAllMethodsInHierarchy, shouldNotUseReservedWords, shouldNotDuplicateEntities })),
-  when(Singleton)(() => ({ nameShouldBeginWithLowercase, inlineSingletonShouldBeAnonymous, topLevelSingletonShouldHaveAName, nameShouldNotBeKeyword, shouldInitializeAllAttributes, linearizationShouldNotRepeatNamedArguments, shouldNotDefineMoreThanOneSuperclass, superclassShouldBeLastInLinearization, shouldNotDuplicateGlobalDefinitions, shouldNotDuplicateVariablesInLinearization, shouldImplementAbstractMethods, shouldImplementAllMethodsInHierarchy, shouldNotUseReservedWords, shouldNotDuplicateEntities })),
+  when(Singleton)(() => ({ nameShouldBeginWithLowercase, inlineSingletonShouldBeAnonymous, topLevelSingletonShouldHaveAName, nameShouldNotBeKeyword, shouldInitializeInheritedAttributes, linearizationShouldNotRepeatNamedArguments, shouldNotDefineMoreThanOneSuperclass, superclassShouldBeLastInLinearization, shouldNotDuplicateGlobalDefinitions, shouldNotDuplicateVariablesInLinearization, shouldImplementAbstractMethods, shouldImplementAllMethodsInHierarchy, shouldNotUseReservedWords, shouldNotDuplicateEntities })),
   when(Mixin)(() => ({ nameShouldBeginWithUppercase, shouldNotHaveLoopInHierarchy, shouldOnlyInheritFromMixin, shouldNotDuplicateGlobalDefinitions, shouldNotDuplicateVariablesInLinearization, shouldNotDuplicateEntities })),
-  when(Field)(() => ({ nameShouldBeginWithLowercase, shouldNotAssignToItselfInDeclaration, nameShouldNotBeKeyword, shouldNotDuplicateFields, shouldNotUseReservedWords, shouldNotDefineUnusedVariables, shouldDefineConstInsteadOfVar })),
+  when(Field)(() => ({ nameShouldBeginWithLowercase, shouldNotAssignToItselfInDeclaration, nameShouldNotBeKeyword, shouldNotDuplicateFields, shouldNotUseReservedWords, shouldNotDefineUnusedVariables, shouldDefineConstInsteadOfVar, shouldInitializeSingletonAttribute })),
   when(Method)(() => ({ onlyLastParameterCanBeVarArg, nameShouldNotBeKeyword, methodShouldHaveDifferentSignature, shouldNotOnlyCallToSuper, shouldUseOverrideKeyword, possiblyReturningBlock, shouldNotUseOverride, shouldMatchSuperclassReturnValue, shouldNotDefineNativeMethodsOnUnnamedSingleton, overridingMethodShouldHaveABody, getterMethodShouldReturnAValue })),
   when(Variable)(() => ({ nameShouldBeginWithLowercase, nameShouldNotBeKeyword, shouldNotAssignToItselfInDeclaration, shouldNotDuplicateLocalVariables, shouldNotDuplicateGlobalDefinitions, shouldNotDefineGlobalMutableVariables, shouldNotUseReservedWords, shouldInitializeGlobalReference, shouldDefineConstInsteadOfVar, shouldNotDuplicateEntities })),
   when(Assignment)(() => ({ shouldNotAssignToItself, shouldNotReassignConst })),
diff --git a/test/validator.test.ts b/test/validator.test.ts
index 51751f30..6eb705e6 100644
--- a/test/validator.test.ts
+++ b/test/validator.test.ts
@@ -4,9 +4,9 @@ import { readFileSync } from 'fs'
 import globby from 'globby'
 import { join } from 'path'
 import { Annotation, buildEnvironment } from '../src'
-import { notEmpty } from '../src/extensions'
+import { List, notEmpty } from '../src/extensions'
 import validate from '../src/validator'
-import { Node, Problem } from './../src/model'
+import { Class, Literal, Node, Problem, Reference } from './../src/model'
 
 const TESTS_PATH = 'language/test/validations'
 
@@ -50,6 +50,7 @@ describe('Wollok Validations', () => {
         for (const expectedProblem of expectedProblems) {
           const code = expectedProblem.args.get('code')!
           const level = expectedProblem.args.get('level')
+          const values = expectedProblem.args.get('values')
 
           if (!code) fail('Missing required "code" argument in @Expect annotation')
 
@@ -64,6 +65,12 @@ describe('Wollok Validations', () => {
 
           if (level && effectiveProblem.level !== level)
             fail(`Expected ${code} to be ${level} but was ${effectiveProblem.level} at ${errorLocation(node)}`)
+
+          if (values) {
+            const stringValues = (values as [Reference<Class>, List<Literal<string>>])[1].map(v => v.value)
+            if (stringValues.join('||') !== effectiveProblem.values.join('||'))
+              fail(`Expected ${code} to have ${JSON.stringify(stringValues)} but was ${JSON.stringify(effectiveProblem.values)} at ${errorLocation(node)}`)
+          }
         }
 
         for (const problem of problems) {