diff --git a/eth/api_backend.go b/eth/api_backend.go
index 78b9b08ecb32..643f6369df0e 100644
--- a/eth/api_backend.go
+++ b/eth/api_backend.go
@@ -75,6 +75,9 @@ func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumb
 		return b.eth.blockchain.CurrentBlock(), nil
 	}
 	if number == rpc.FinalizedBlockNumber {
+		if !b.eth.Merger().TDDReached() {
+			return nil, errors.New("'finalized' tag not supported on pre-merge network")
+		}
 		block := b.eth.blockchain.CurrentFinalBlock()
 		if block != nil {
 			return block, nil
@@ -82,6 +85,9 @@ func (b *EthAPIBackend) HeaderByNumber(ctx context.Context, number rpc.BlockNumb
 		return nil, errors.New("finalized block not found")
 	}
 	if number == rpc.SafeBlockNumber {
+		if !b.eth.Merger().TDDReached() {
+			return nil, errors.New("'safe' tag not supported on pre-merge network")
+		}
 		block := b.eth.blockchain.CurrentSafeBlock()
 		if block != nil {
 			return block, nil
@@ -124,10 +130,16 @@ func (b *EthAPIBackend) BlockByNumber(ctx context.Context, number rpc.BlockNumbe
 		return b.eth.blockchain.GetBlock(header.Hash(), header.Number.Uint64()), nil
 	}
 	if number == rpc.FinalizedBlockNumber {
+		if !b.eth.Merger().TDDReached() {
+			return nil, errors.New("'finalized' tag not supported on pre-merge network")
+		}
 		header := b.eth.blockchain.CurrentFinalBlock()
 		return b.eth.blockchain.GetBlock(header.Hash(), header.Number.Uint64()), nil
 	}
 	if number == rpc.SafeBlockNumber {
+		if !b.eth.Merger().TDDReached() {
+			return nil, errors.New("'safe' tag not supported on pre-merge network")
+		}
 		header := b.eth.blockchain.CurrentSafeBlock()
 		return b.eth.blockchain.GetBlock(header.Hash(), header.Number.Uint64()), nil
 	}