diff --git a/build.py b/build.py
index 29ecee9..d5d07d4 100755
--- a/build.py
+++ b/build.py
@@ -60,7 +60,7 @@ def build_index(yaml, prefix):
 
     l_index = []
     for i, item in enumerate(l_title):
-        l_index += [' - ' + item.ljust(MAX_WIDTH - 10) + f'[{prefix}{i+1}00] ']
+        l_index += [' - ' + item.ljust(MAX_WIDTH - 10) + f'[{prefix}{i+1:03}] ']
 
     l_index += [' ' * MAX_WIDTH]