diff --git a/src/rustint/core.clj b/src/rustint/core.clj
index 5ed5e00..319c54b 100644
--- a/src/rustint/core.clj
+++ b/src/rustint/core.clj
@@ -2279,12 +2279,7 @@
   (and
     (symbol?  arg)
     (not (palabra-reservada? arg))
-    (contains?
-      (set
-        (map char (range 97 122))
-      )
-      (first (name arg))
-    )
+    (not (nil? (re-matches #"_?[a-zA-Z][a-zA-Z0-9]*" (name arg))))
   )
 )