Index: trunk/src/org/openstreetmap/josm/gui/io/UploadDialogModel.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/io/UploadDialogModel.java	(revision 18202)
+++ trunk/src/org/openstreetmap/josm/gui/io/UploadDialogModel.java	(revision 18205)
@@ -75,5 +75,5 @@
             Arrays.stream(comment.split("\\s", -1))
                 .map(s -> Utils.strip(s, ",;"))
-                .filter(s -> s.matches("#[a-zA-Z][-_a-zA-Z0-9]+"))
+                .filter(s -> s.matches("#[a-zA-Z0-9][-_a-zA-Z0-9]+"))
                 .collect(Collectors.toList()));
         return hashtags.isEmpty() ? null : hashtags;