diff --git a/app/controllers/poll/participation.js b/app/controllers/poll/participation.js
index b90b845..c39f5fb 100644
--- a/app/controllers/poll/participation.js
+++ b/app/controllers/poll/participation.js
@@ -12,18 +12,29 @@ const validCollection = function(collection) {
   });
 };
 const Validations = buildValidations({
-  name: validator('presence', {
-    presence() {
-      // only force presence if anonymousUser poll setting is false
-      if (!this.get('model.anonymousUser')) {
-        return true;
-      } else {
-        // disable presence validation
-        return null;
-      }
-    },
-    dependentKeys: ['anonymousUser', 'i18n.locale']
-  }),
+  name: [
+    validator('presence', {
+      presence() {
+        // only force presence if anonymousUser poll setting is false
+        if (!this.get('model.anonymousUser')) {
+          return true;
+        } else {
+          // disable presence validation
+          return null;
+        }
+      },
+      dependentKeys: ['anonymousUser', 'i18n.locale']
+    }),
+    validator('unique', {
+      parent: 'pollController.model',
+      attributeInParent: 'users',
+      dependentKeys: ['poll.users.[]', 'poll.users.@each.name', 'i18n.locale'],
+      disable() {
+        return this.get('model.anonymousUser');
+      },
+      messageKey: 'unique.name'
+    })
+  ],
 
   selections: [
     validator('collection', true),
diff --git a/app/locales/de/translations.js b/app/locales/de/translations.js
index 745d17f..a03fa61 100644
--- a/app/locales/de/translations.js
+++ b/app/locales/de/translations.js
@@ -125,6 +125,7 @@ export default {
     phone: '{{description}} muss eine gültige Telefonnummer sein',
     url: '{{description}} muss eine gültige URL sein',
     time: '{{value}} muss eine gültige Zeit sein',
-    unique: '{{description}} muss eindeutig sein'
+    unique: '{{description}} muss eindeutig sein',
+    'unique.name': 'Dieser Namen wurde bereits genutzt'
   }
 };
diff --git a/app/locales/en/translations.js b/app/locales/en/translations.js
index 64a0a8e..9c6ab05 100644
--- a/app/locales/en/translations.js
+++ b/app/locales/en/translations.js
@@ -125,6 +125,7 @@ export default {
     phone: '{{description}} must be a valid phone mumber',
     url: '{{description}} must be a valid URL ',
     time: '{{value}} must be a valid number',
-    unique: '{{description}} must be explicit'
+    unique: '{{description}} must be explicit',
+    'unique.name': 'This name has already been used'
   }
 };
diff --git a/app/locales/es/translations.js b/app/locales/es/translations.js
index 8fd7d2d..f724c7b 100644
--- a/app/locales/es/translations.js
+++ b/app/locales/es/translations.js
@@ -125,6 +125,7 @@ export default {
     phone: '{{description}} must be a valid phone number',
     url: '{{description}} must be a valid url',
     time: '{{value}} must be a valid time',
-    unique: '{{description}} must be unique'
+    unique: '{{description}} must be unique',
+    'unique.name': 'This name has already been used'
   }
 };
diff --git a/app/validators/unique.js b/app/validators/unique.js
index c80e473..9360bde 100644
--- a/app/validators/unique.js
+++ b/app/validators/unique.js
@@ -16,20 +16,25 @@ export default BaseValidator.extend({
       Ember.isArray(options.dependentKeys) && options.dependentKeys.length > 0
     );
 
+    if (options.disable) {
+      return true;
+    }
+
     // ignore empty values
     if (Ember.isEmpty(value)) {
       return true;
     }
 
+    const messageKey = options.messageKey || 'unique';
     const parent = model.get(options.parent);
     const collection = parent.get(options.attributeInParent);
     const positionInCollection = collection.indexOf(model);
-    const elementsBefore = collection.slice(0, positionInCollection);
+    const elementsBefore = positionInCollection !== -1 ? collection.slice(0, positionInCollection) : collection;
     const matches = elementsBefore.findBy(attribute, value);
 
     if (matches) {
       // ToDo: translateable error message
-      return this.createErrorMessage('unique');
+      return this.createErrorMessage(messageKey);
     } else {
       return true;
     }