diff --git a/src/main/java/org/jabref/gui/mergeentries/FetchAndMergeEntry.java b/src/main/java/org/jabref/gui/mergeentries/FetchAndMergeEntry.java
index dbe205a24c4..c14e0770c15 100644
--- a/src/main/java/org/jabref/gui/mergeentries/FetchAndMergeEntry.java
+++ b/src/main/java/org/jabref/gui/mergeentries/FetchAndMergeEntry.java
@@ -40,6 +40,7 @@
  */
 public class FetchAndMergeEntry {
 
+    // All identifiers listed here should also appear at {@link org.jabref.logic.importer.CompositeIdFetcher#performSearchById}
     public static List<Field> SUPPORTED_FIELDS = Arrays.asList(StandardField.DOI, StandardField.EPRINT, StandardField.ISBN);
 
     private static final Logger LOGGER = LoggerFactory.getLogger(FetchAndMergeEntry.class);
diff --git a/src/main/java/org/jabref/logic/importer/CompositeIdFetcher.java b/src/main/java/org/jabref/logic/importer/CompositeIdFetcher.java
index 83d939a3085..ffde24b1af9 100644
--- a/src/main/java/org/jabref/logic/importer/CompositeIdFetcher.java
+++ b/src/main/java/org/jabref/logic/importer/CompositeIdFetcher.java
@@ -20,6 +20,8 @@ public CompositeIdFetcher(ImportFormatPreferences importFormatPreferences) {
     }
 
     public Optional<BibEntry> performSearchById(String identifier) throws FetcherException {
+        // All identifiers listed here should also be appear at {@link org.jabref.gui.mergeentries.FetchAndMergeEntry.SUPPORTED_FIELDS} and vice versa.
+
         Optional<DOI> doi = DOI.findInText(identifier);
         if (doi.isPresent()) {
             return new DoiFetcher(importFormatPreferences).performSearchById(doi.get().getNormalized());