diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -1457,6 +1457,8 @@
         sigHashType = sigHashType.withForkValue(0xff0000 | newForkValue);
     }
 
+    assert(nIn < txTo.vin.size());
+
     if (sigHashType.hasForkId() && (flags & SCRIPT_ENABLE_SIGHASH_FORKID)) {
         uint256 hashPrevouts;
         uint256 hashSequence;
@@ -1507,10 +1509,6 @@
 
     static const uint256 one(uint256S(
         "0000000000000000000000000000000000000000000000000000000000000001"));
-    if (nIn >= txTo.vin.size()) {
-        //  nIn out of range
-        return one;
-    }
 
     // Check for invalid use of SIGHASH_SINGLE
     if ((sigHashType.getBaseType() == BaseSigHashType::SINGLE) &&