diff --git a/tests/ethprocs.nim b/tests/ethprocs.nim
index 215d097..d54ea9c 100644
--- a/tests/ethprocs.nim
+++ b/tests/ethprocs.nim
@@ -1,4 +1,4 @@
-import ../rpcserver, nimcrypto, json, stint, strutils, ethtypes, stintjson
+import ../rpcserver, nimcrypto, json, stint, strutils, ethtypes, stintjson, ethutils
 
 #[
   For details on available RPC calls, see: https://github.com/ethereum/wiki/wiki/JSON-RPC
@@ -38,10 +38,10 @@ proc addEthRpcs*(server: RpcServer) =
     ## Returns the SHA3 result of the given string.
     # TODO: Capture error on malformed input
     var rawData: seq[byte]
-    if data.len > 2 and data[0] == '0' and data[1] in ['x', 'X']:
+    if data.validateHexData:
       rawData = data[2..data.high].fromHex
     else:
-      rawData = data.fromHex
+      raise newException(ValueError, "Invalid hex format")
     # data will have 0x prefix
     result = "0x" & $keccak_256.digest(rawData)