Index: trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadNotesTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadNotesTask.java	(revision 15357)
+++ trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadNotesTask.java	(revision 15358)
@@ -49,4 +49,8 @@
 
     private static final String PATTERN_COMPRESS = "https?://.*/(.*\\.osn.(gz|xz|bz2?|zip))";
+    private static final String NO_NOTES_FOUND = tr("No notes found in this area.");
+    static {
+        PostDownloadHandler.addNoDataErrorMessage(NO_NOTES_FOUND);
+    }
 
     private DownloadTask downloadTask;
@@ -133,5 +137,5 @@
             if (notesData.isEmpty()) {
                 if (warnAboutEmptyArea) {
-                    rememberErrorMessage(tr("No notes found in this area."));
+                    rememberErrorMessage(NO_NOTES_FOUND);
                 }
                 return;
Index: trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadOsmTask.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadOsmTask.java	(revision 15357)
+++ trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadOsmTask.java	(revision 15358)
@@ -63,4 +63,9 @@
 
     protected static final String OVERPASS_INTERPRETER_DATA = "interpreter?data=";
+
+    private static final String NO_DATA_FOUND = tr("No data found in this area.");
+    static {
+        PostDownloadHandler.addNoDataErrorMessage(NO_DATA_FOUND);
+    }
 
     @Override
@@ -466,5 +471,5 @@
             if (dataSet.allPrimitives().isEmpty()) {
                 if (warnAboutEmptyArea) {
-                    rememberErrorMessage(tr("No data found in this area."));
+                    rememberErrorMessage(NO_DATA_FOUND);
                 }
                 String remark = dataSet.getRemark();
Index: trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadTaskList.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadTaskList.java	(revision 15357)
+++ trunk/src/org/openstreetmap/josm/actions/downloadtasks/DownloadTaskList.java	(revision 15358)
@@ -264,5 +264,5 @@
 
                 GuiHelper.runInEDT(() -> {
-                    if (items.size() == 1 && tr("No data found in this area.").equals(items.iterator().next())) {
+                    if (items.size() == 1 && PostDownloadHandler.isNoDataErrorMessage(items.iterator().next())) {
                         new Notification(items.iterator().next()).setIcon(JOptionPane.WARNING_MESSAGE).show();
                     } else {
Index: trunk/src/org/openstreetmap/josm/actions/downloadtasks/PostDownloadHandler.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/downloadtasks/PostDownloadHandler.java	(revision 15357)
+++ trunk/src/org/openstreetmap/josm/actions/downloadtasks/PostDownloadHandler.java	(revision 15358)
@@ -7,4 +7,5 @@
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.LinkedHashSet;
 import java.util.Set;
@@ -34,4 +35,6 @@
     private Consumer<Collection<Object>> errorReporter;
 
+    private static final Set<String> NO_DATA_ERROR_MESSAGES = new HashSet<>();
+
     /**
      * Creates a new {@link PostDownloadHandler}
@@ -54,4 +57,24 @@
         this(task, future);
         this.errorReporter = errorReporter;
+    }
+
+    /**
+     * Adds a new translated error message indicating that no data has been downloaded.
+     * @param message new translated error message indicating that no data has been downloaded.
+     * @return {@code true} if the message was not already known
+     * @since 15358
+     */
+    public static boolean addNoDataErrorMessage(String message) {
+        return NO_DATA_ERROR_MESSAGES.add(message);
+    }
+
+    /**
+     * Determines if a translated error message indicates that no data has been downloaded.
+     * @param message translated error message to check
+     * @return {@code true} if the message indicates that no data has been downloaded
+     * @since 15358
+     */
+    public static boolean isNoDataErrorMessage(Object message) {
+        return NO_DATA_ERROR_MESSAGES.contains(message);
     }
 
@@ -87,5 +110,5 @@
                     if (error instanceof Exception) {
                         ExceptionDialogUtil.explainException((Exception) error);
-                    } else if (tr("No data found in this area.").equals(error)) {
+                    } else if (isNoDataErrorMessage(error)) {
                         new Notification(error.toString()).setIcon(JOptionPane.WARNING_MESSAGE).show();
                     } else {