diff --git a/lib/src/transaction.dart b/lib/src/transaction.dart
index d37bfd7..87c43bd 100644
--- a/lib/src/transaction.dart
+++ b/lib/src/transaction.dart
@@ -560,7 +560,7 @@ class Input {
 
   factory Input.expandInput(Uint8List scriptSig, List<Uint8List> witness,
       [String type, Uint8List scriptPubKey]) {
-    if (type == null || type == '') {
+    if (type == null) {
       var ssType = classifyInput(scriptSig);
       var wsType = classifyWitness(witness);
       if (ssType == SCRIPT_TYPES['NONSTANDARD']) ssType = null;
@@ -588,6 +588,10 @@ class Input {
           pubkeys: [],
           signatures: [p2pk.data.signature]);
     }
+    return Input(
+      prevOutType: SCRIPT_TYPES['NONSTANDARD'],
+      prevOutScript: scriptSig,
+    );
   }
 
   factory Input.clone(Input input) {
diff --git a/lib/src/transaction_builder.dart b/lib/src/transaction_builder.dart
index 2ff61bf..aa9212e 100644
--- a/lib/src/transaction_builder.dart
+++ b/lib/src/transaction_builder.dart
@@ -339,9 +339,8 @@ class TransactionBuilder {
     if (options.script != null) {
       input =
           Input.expandInput(options.script, options.witness ?? EMPTY_WITNESS);
-    } else {
-      input = new Input();
     }
+    if (input == null) input = Input();
     if (options.value != null) input.value = options.value;
     if (input.prevOutScript == null && options.prevOutScript != null) {
       if (input.pubkeys == null && input.signatures == null) {