diff --git a/apertium_apy/mode_search.py b/apertium_apy/mode_search.py
index 95722f4..758affe 100644
--- a/apertium_apy/mode_search.py
+++ b/apertium_apy/mode_search.py
@@ -29,7 +29,7 @@ def is_loop(dirpath, rootpath, real_root=None):
 
 
 def search_path(rootpath, include_pairs=True, verbosity=1):
-    lang_code = r'[a-z]{2,3}(?:_[A-Za-z]+)?'
+    lang_code = r'[a-z]{2,3}(?:_[A-Za-z0-9_]+)?'
     type_re = {
         'pair': re.compile(r'({0})-({0})\.mode'.format(lang_code)),
         'analyzer': re.compile(r'(({0}(-{0})?)-(an)?mor(ph)?)\.mode'.format(lang_code)),