diff --git a/src/albireo.pest b/src/albireo.pest
index b11cc3a..099c354 100644
--- a/src/albireo.pest
+++ b/src/albireo.pest
@@ -26,7 +26,7 @@ keywords   =  {
 
 // if identifier starts with something like a keyword, it must follows something else
 // in any case, the identifier cannot begin with a digit
-identifier = @{ keywords? ~ ("_" | ASCII_ALPHANUMERIC)+
+identifier = @{ keywords ~ ("_" | ASCII_ALPHANUMERIC)+
                 | !keywords ~ ASCII_ALPHA ~ ("_" | ASCII_ALPHANUMERIC)* }
 
 function_type_param  =  { type* }