diff --git a/interfaces.go b/interfaces.go
index 21d42c6d347..5267c9ad997 100644
--- a/interfaces.go
+++ b/interfaces.go
@@ -278,6 +278,8 @@ type PendingContractCaller interface {
 // it should provide a basis for setting a reasonable default.
 type GasEstimator interface {
 	EstimateGas(ctx context.Context, call CallMsg) (uint64, error)
+	EstimateGasAtBlock(ctx context.Context, call CallMsg, blockNumber *big.Int) (uint64, error)
+	EstimateGasAtBlockHash(ctx context.Context, call CallMsg, blockHash common.Hash) (uint64, error)
 }
 
 // A PendingStateEventer provides access to real time notifications about changes to the
@@ -296,6 +298,11 @@ type ChainIDReader interface {
 	ChainID(ctx context.Context) (*big.Int, error)
 }
 
+// NetworkIDReader provides access to the network ID.
+type NetworkIDReader interface {
+	NetworkID(ctx context.Context) (*big.Int, error)
+}
+
 // OverrideAccount specifies the state of an account to be overridden.
 type OverrideAccount struct {
 	// Nonce sets nonce of the account. Note: the nonce override will only