diff --git a/cumulus/client/network/src/tests.rs b/cumulus/client/network/src/tests.rs
index ce2246f04c..d2def635b5 100644
--- a/cumulus/client/network/src/tests.rs
+++ b/cumulus/client/network/src/tests.rs
@@ -242,9 +242,12 @@ impl RelayChainInterface for DummyRelayChainInterface {
 	async fn header(&self, block_id: BlockId) -> RelayChainResult<Option<PHeader>> {
 		let hash = match block_id {
 			BlockId::Hash(hash) => hash,
-			BlockId::Number(num) => self.relay_client.hash(num)?.ok_or_else(|| {
-				RelayChainError::GenericError(format!("block with number {num} not found"))
-			})?,
+			BlockId::Number(num) =>
+				if let Some(hash) = self.relay_client.hash(num)? {
+					hash
+				} else {
+					return Ok(None)
+				},
 		};
 		let header = self.relay_client.header(hash)?;
 
diff --git a/cumulus/client/relay-chain-inprocess-interface/src/lib.rs b/cumulus/client/relay-chain-inprocess-interface/src/lib.rs
index cc522ba4d3..54b0362a47 100644
--- a/cumulus/client/relay-chain-inprocess-interface/src/lib.rs
+++ b/cumulus/client/relay-chain-inprocess-interface/src/lib.rs
@@ -94,9 +94,12 @@ impl RelayChainInterface for RelayChainInProcessInterface {
 	async fn header(&self, block_id: BlockId) -> RelayChainResult<Option<PHeader>> {
 		let hash = match block_id {
 			BlockId::Hash(hash) => hash,
-			BlockId::Number(num) => self.full_client.hash(num)?.ok_or_else(|| {
-				RelayChainError::GenericError(format!("block with number {num} not found"))
-			})?,
+			BlockId::Number(num) =>
+				if let Some(hash) = self.full_client.hash(num)? {
+					hash
+				} else {
+					return Ok(None)
+				},
 		};
 		let header = self.full_client.header(hash)?;
 
diff --git a/cumulus/client/relay-chain-rpc-interface/src/lib.rs b/cumulus/client/relay-chain-rpc-interface/src/lib.rs
index 3c6f3ca323..964d47eff9 100644
--- a/cumulus/client/relay-chain-rpc-interface/src/lib.rs
+++ b/cumulus/client/relay-chain-rpc-interface/src/lib.rs
@@ -82,9 +82,11 @@ impl RelayChainInterface for RelayChainRpcInterface {
 		let hash = match block_id {
 			BlockId::Hash(hash) => hash,
 			BlockId::Number(num) =>
-				self.rpc_client.chain_get_block_hash(Some(num)).await?.ok_or_else(|| {
-					RelayChainError::GenericError(format!("block with number {num} not found"))
-				})?,
+				if let Some(hash) = self.rpc_client.chain_get_block_hash(Some(num)).await? {
+					hash
+				} else {
+					return Ok(None)
+				},
 		};
 		let header = self.rpc_client.chain_get_header(Some(hash)).await?;