diff --git a/chain/src/chain.rs b/chain/src/chain.rs
index d244a9405..878b670c0 100644
--- a/chain/src/chain.rs
+++ b/chain/src/chain.rs
@@ -438,7 +438,7 @@ impl Chain {
 	/// current chain state, specifically the current winning (valid, most
 	/// work) fork.
 	pub fn is_unspent(&self, output_ref: &OutputIdentifier) -> Result<Hash, Error> {
-		let mut txhashset = self.txhashset.write();
+		let txhashset = self.txhashset.read();
 		let res = txhashset.is_unspent(output_ref);
 		match res {
 			Err(e) => Err(e),
@@ -1096,7 +1096,7 @@ impl Chain {
 		output_ref: &OutputIdentifier,
 	) -> Result<BlockHeader, Error> {
 		let pos = {
-			let mut txhashset = self.txhashset.write();
+			let txhashset = self.txhashset.read();
 			let (_, pos) = txhashset.is_unspent(output_ref)?;
 			pos
 		};
diff --git a/chain/src/txhashset/txhashset.rs b/chain/src/txhashset/txhashset.rs
index d7114fb5d..09d7c96da 100644
--- a/chain/src/txhashset/txhashset.rs
+++ b/chain/src/txhashset/txhashset.rs
@@ -160,11 +160,11 @@ impl TxHashSet {
 	/// Check if an output is unspent.
 	/// We look in the index to find the output MMR pos.
 	/// Then we check the entry in the output MMR and confirm the hash matches.
-	pub fn is_unspent(&mut self, output_id: &OutputIdentifier) -> Result<(Hash, u64), Error> {
+	pub fn is_unspent(&self, output_id: &OutputIdentifier) -> Result<(Hash, u64), Error> {
 		match self.commit_index.get_output_pos(&output_id.commit) {
 			Ok(pos) => {
-				let output_pmmr: PMMR<Output, _> =
-					PMMR::at(&mut self.output_pmmr_h.backend, self.output_pmmr_h.last_pos);
+				let output_pmmr: ReadonlyPMMR<Output, _> =
+					ReadonlyPMMR::at(&self.output_pmmr_h.backend, self.output_pmmr_h.last_pos);
 				if let Some(hash) = output_pmmr.get_hash(pos) {
 					if hash == output_id.hash_with_index(pos - 1) {
 						Ok((hash, pos))
diff --git a/core/src/core/pmmr/readonly_pmmr.rs b/core/src/core/pmmr/readonly_pmmr.rs
index a9a3a7562..e4557b3d5 100644
--- a/core/src/core/pmmr/readonly_pmmr.rs
+++ b/core/src/core/pmmr/readonly_pmmr.rs
@@ -16,6 +16,7 @@
 
 use std::marker;
 
+use core::hash::Hash;
 use core::pmmr::{is_leaf, Backend};
 use ser::PMMRable;
 
@@ -70,4 +71,17 @@ where
 			None
 		}
 	}
+
+	/// Get the hash at provided position in the MMR.
+	pub fn get_hash(&self, pos: u64) -> Option<Hash> {
+		if pos > self.last_pos {
+			None
+		} else if is_leaf(pos) {
+			// If we are a leaf then get hash from the backend.
+			self.backend.get_hash(pos)
+		} else {
+			// If we are not a leaf get hash ignoring the remove log.
+			self.backend.get_from_file(pos)
+		}
+	}
 }