diff --git a/verification/src/chain_verifier.rs b/verification/src/chain_verifier.rs
index 6c385c14..8ea15955 100644
--- a/verification/src/chain_verifier.rs
+++ b/verification/src/chain_verifier.rs
@@ -34,7 +34,7 @@ impl ChainVerifier {
 				None => {
 					match block.transactions.iter().filter(|t| t.hash() == input.previous_output.hash).nth(0) {
 						Some(ref tx) => tx,
-						None => { return Err(TransactionError::Input(input_index)); },
+						None => { return Err(TransactionError::Inconclusive(input.previous_output.hash.clone())); },
 					}
 				},
 			};
@@ -111,7 +111,7 @@ impl Verify for ChainVerifier {
 mod tests {
 
 	use super::ChainVerifier;
-	use super::super::{Verify, Chain};
+	use super::super::{Verify, Chain, Error, TransactionError};
 	use db::TestStorage;
 	use test_data;
 	use std::sync::Arc;
@@ -146,4 +146,21 @@ mod tests {
 		assert_eq!(Chain::Main, verifier.verify(&b1).unwrap());
 	}
 
+	#[test]
+	fn unknown_transaction_returns_inconclusive() {
+		let storage = TestStorage::with_blocks(
+			&vec![
+				test_data::block_h169(),
+			]
+		);
+		let b170 = test_data::block_h170();
+		let verifier = ChainVerifier::new(Arc::new(storage));
+
+		let should_be = Err(Error::Transaction(
+			0,
+			TransactionError::Inconclusive("c997a5e56e104102fa209c6a852dd90660a20b2d9c352423edce25857fcd3704".into())
+		));
+		assert_eq!(should_be, verifier.verify(&b170));
+	}
+
 }
diff --git a/verification/src/lib.rs b/verification/src/lib.rs
index 273102c1..3e6b708c 100644
--- a/verification/src/lib.rs
+++ b/verification/src/lib.rs
@@ -22,7 +22,9 @@ mod chain_verifier;
 pub use queue::Queue;
 pub use chain_verifier::ChainVerifier;
 
-#[derive(Debug)]
+use primitives::hash::H256;
+
+#[derive(Debug, PartialEq)]
 /// All possible verification errors
 pub enum Error {
 	/// has an equal duplicate in the chain
@@ -43,7 +45,7 @@ pub enum Error {
 	MerkleRoot,
 }
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 /// Possible transactions verification errors
 pub enum TransactionError {
 	/// Not found corresponding output for transaction input
@@ -52,6 +54,8 @@ pub enum TransactionError {
 	Maturity,
 	/// Signature invalid for given input
 	Signature(usize),
+	/// Inconclusive (unknown parent transaction)
+	Inconclusive(H256),
 }
 
 #[derive(PartialEq, Debug)]