diff --git a/manticore/ethereum.py b/manticore/ethereum.py
index <HASH>..<HASH> 100644
--- a/manticore/ethereum.py
+++ b/manticore/ethereum.py
@@ -613,7 +613,7 @@ class ABI(object):
         '''
         Build transaction data from function signature and arguments
         '''
-        m = re.match(r"(?P<name>[a-zA-Z_]+)(?P<type>\(.*\))", type_spec)
+        m = re.match(r"(?P<name>[a-zA-Z_][a-zA-Z_0-9]*)(?P<type>\(.*\))", type_spec)
         if not m:
             raise EthereumError("Function signature expected")
Allow function identifiers on smart contract to have numbers on them (#<I>)