diff --git a/lib/transaction/input/input.js b/lib/transaction/input/input.js
index 366a3f7..1255a71 100644
--- a/lib/transaction/input/input.js
+++ b/lib/transaction/input/input.js
@@ -125,7 +125,10 @@ Input.prototype.setScript = function(script) {
  * @abstract
  */
 Input.prototype.getSignatures = function() {
-  throw new errors.AbstractMethodInvoked('Input#getSignatures');
+  throw new errors.AbstractMethodInvoked(
+    'Trying to sign unsupported output type (only P2PKH and P2SH multisig inputs are supported)' +
+    ' for input: ' + this.toJSON()
+  );
 };
 
 Input.prototype.isFullySigned = function() {