diff --git a/src/Form/Settings/TypeSynonymsCollectionType.php b/src/Form/Settings/TypeSynonymsCollectionType.php
index dacacfdf..9c95db82 100644
--- a/src/Form/Settings/TypeSynonymsCollectionType.php
+++ b/src/Form/Settings/TypeSynonymsCollectionType.php
@@ -88,6 +88,8 @@ class TypeSynonymsCollectionType extends AbstractType
             function (array $viewValue) {
                 //Turn our flat list back into the structured array
 
+                $out = [];
+
                 foreach ($viewValue as $row) {
                     if (!is_array($row)) {
                         continue;
@@ -133,8 +135,8 @@ class TypeSynonymsCollectionType extends AbstractType
                 $ds = $row['dataSource'] ?? null;
                 $loc = $row['locale'] ?? null;
 
-                if (is_string($ds) && $ds !== '' && is_string($loc) && $loc !== '') {
-                    $key = $ds . '|' . $loc;
+                if ($ds !== null && is_string($loc) && $loc !== '') {
+                    $key = $ds->value . '|' . $loc;
                     if (isset($seen[$key])) {
                         $hasDuplicate = true;
 
diff --git a/translations/validators.en.xlf b/translations/validators.en.xlf
index 6ad14460..86045227 100644
--- a/translations/validators.en.xlf
+++ b/translations/validators.en.xlf
@@ -347,13 +347,13 @@
         <target>Due to technical limitations, it is not possible to select dates after the 2038-01-19 on 32-bit systems!</target>
       </segment>
     </unit>
-    <unit id="89nojXY" name="validator.fileSize.invalidFormat">
+    <unit id="iM9yb_p" name="validator.fileSize.invalidFormat">
       <segment state="translated">
         <source>validator.fileSize.invalidFormat</source>
         <target>Invalid file size format. Use an integer number plus K, M, G as suffix for Kilo, Mega or Gigabytes.</target>
       </segment>
     </unit>
-    <unit id="iXcU7ce" name="validator.invalid_range">
+    <unit id="ZFxQ0BZ" name="validator.invalid_range">
       <segment state="translated">
         <source>validator.invalid_range</source>
         <target>The given range is not valid!</target>
@@ -365,5 +365,11 @@
         <target>Invalid code. Check that your authenticator app is set up correctly and that both the server and authentication device has the time set correctly.</target>
       </segment>
     </unit>
+    <unit id="I330cr5" name="settings.synonyms.type_synonyms.collection_type.duplicate">
+      <segment>
+        <source>settings.synonyms.type_synonyms.collection_type.duplicate</source>
+        <target>There is already a translation defined for this type and language!</target>
+      </segment>
+    </unit>
   </file>
 </xliff>