diff --git a/ethcore/src/error.rs b/ethcore/src/error.rs
index dd4cf4986..aae224116 100644
--- a/ethcore/src/error.rs
+++ b/ethcore/src/error.rs
@@ -86,9 +86,6 @@ pub enum BlockError {
 	TemporarilyInvalid(OutOfBounds<u64>),
 	/// Log bloom header field is invalid.
 	InvalidLogBloom(Mismatch<Bloom>),
-	/// Parent hash field of header is invalid; this is an invalid error indicating a logic flaw in the codebase.
-	/// TODO: remove and favour an assert!/panic!.
-	InvalidParentHash(Mismatch<H256>),
 	/// Number field of header is invalid.
 	InvalidNumber(Mismatch<BlockNumber>),
 	/// Block number isn't sensible.
@@ -131,7 +128,6 @@ impl fmt::Display for BlockError {
 			InvalidTimestamp(ref oob) => format!("Invalid timestamp in header: {}", oob),
 			TemporarilyInvalid(ref oob) => format!("Future timestamp in header: {}", oob),
 			InvalidLogBloom(ref oob) => format!("Invalid log bloom in header: {}", oob),
-			InvalidParentHash(ref mis) => format!("Invalid parent hash: {}", mis),
 			InvalidNumber(ref mis) => format!("Invalid number in header: {}", mis),
 			RidiculousNumber(ref oob) => format!("Implausible block number. {}", oob),
 			UnknownParent(ref hash) => format!("Unknown parent: {}", hash),
diff --git a/ethcore/src/verification/verification.rs b/ethcore/src/verification/verification.rs
index b670851f0..e6289c2b0 100644
--- a/ethcore/src/verification/verification.rs
+++ b/ethcore/src/verification/verification.rs
@@ -304,11 +304,11 @@ pub fn verify_header_params(header: &Header, engine: &EthEngine, is_full: bool)
 
 /// Check header parameters agains parent header.
 fn verify_parent(header: &Header, parent: &Header, engine: &EthEngine) -> Result<(), Error> {
+	assert!(header.parent_hash().is_zero() || &parent.hash() == header.parent_hash(),
+			"Parent hash should already have been verified; qed");
+
 	let gas_limit_divisor = engine.params().gas_limit_bound_divisor;
 
-	if !header.parent_hash().is_zero() && &parent.hash() != header.parent_hash() {
-		return Err(From::from(BlockError::InvalidParentHash(Mismatch { expected: parent.hash(), found: header.parent_hash().clone() })))
-	}
 	if !engine.is_timestamp_valid(header.timestamp(), parent.timestamp()) {
 		return Err(From::from(BlockError::InvalidTimestamp(OutOfBounds { max: None, min: Some(parent.timestamp() + 1), found: header.timestamp() })))
 	}