diff --git a/dlibrary/dlibrary.py b/dlibrary/dlibrary.py
index ef8bbb8..4e2eea6 100755
--- a/dlibrary/dlibrary.py
+++ b/dlibrary/dlibrary.py
@@ -245,26 +245,31 @@ def complete_prefix_number_ordering(entries):
     return result
 
 def unique_hierarchical_prefix_numbering(entries, start_point=0):
-    matches = reversed(list(NUMBER_REGEX.finditer(entries[0].name)))
+    longest_entry = max(entries, key=lambda e: len(e.name))
+    matches = reversed(list(NUMBER_REGEX.finditer(longest_entry.name)))
     for m in matches:
         pos = m.start()
         if pos < start_point:
             return None
-        prefix = entries[0].name[:pos]
-        if all(e.name.startswith(prefix) for e in entries):
+        prefix = longest_entry.name[:pos]
+        if all(e.name.startswith(prefix) or prefix.startswith(e.stem) for e in entries):
             numbering = {}
             for e in entries:
-                n = NUMBER_REGEX.match(e.name[pos:])
-                if n is None:
-                    return None
-                i = int(n.group())
+                if pos >= len(e.stem):
+                    i = 0
+                else:
+                    n = NUMBER_REGEX.match(e.name[pos:])
+                    if n is None:
+                        return None
+                    i = int(n.group())
                 numbering.setdefault((i,), []).append(e)
 
             indices = list(numbering.keys())
             for idx in indices:
                 if len(numbering[idx]) > 1:
                     ents_idx = numbering.pop(idx)
-                    next_layer_start = pos + NUMBER_REGEX.match(ents_idx[0].name[pos:]).end()
+                    longest = max(ents_idx, key=lambda e: len(e.name))
+                    next_layer_start = pos + NUMBER_REGEX.match(longest.name[pos:]).end()
                     sub_numbering = unique_hierarchical_prefix_numbering(ents_idx, start_point=next_layer_start) or alphabetic_numbering(ents_idx, next_layer_start)
                     if not sub_numbering:
                         return None