diff --git a/test/functional/fundrawtransaction.py b/test/functional/fundrawtransaction.py
--- a/test/functional/fundrawtransaction.py
+++ b/test/functional/fundrawtransaction.py
@@ -653,7 +653,8 @@
             rawtx, {"feeRate": 2 * min_relay_tx_fee})
         result3 = self.nodes[3].fundrawtransaction(
             rawtx, {"feeRate": 10 * min_relay_tx_fee})
-        result_fee_rate = result['fee'] * 1000 / count_bytes(result['hex'])
+        result_fee_rate = result['fee'] * 1000 / \
+            FromHex(CTransaction(), result['hex']).billable_size()
         assert_fee_amount(
             result2['fee'], FromHex(CTransaction(), result2['hex']).billable_size(), 2 * result_fee_rate)
         assert_fee_amount(