diff --git a/apertium_apy/utils/__init__.py b/apertium_apy/utils/__init__.py
index b3152c4..c403229 100644
--- a/apertium_apy/utils/__init__.py
+++ b/apertium_apy/utils/__init__.py
@@ -30,7 +30,7 @@ def run_async_thread(func):
 
 def to_alpha2_code(code):
     if '_' in code:
-        code, variant = code.split('_')
+        code, variant = code.split('_', 1)
         return '%s_%s' % ((iso639Codes[code], variant) if code in iso639Codes else (code, variant))
     else:
         return iso639Codes[code] if code in iso639Codes else code
@@ -39,7 +39,7 @@ def to_alpha2_code(code):
 def to_alpha3_code(code):
     iso639_codes_inverse = {v: k for k, v in iso639Codes.items()}
     if '_' in code:
-        code, variant = code.split('_')
+        code, variant = code.split('_', 1)
         return '%s_%s' % ((iso639_codes_inverse[code], variant) if code in iso639_codes_inverse else (code, variant))
     else:
         return iso639_codes_inverse[code] if code in iso639_codes_inverse else code