diff --git a/CHANGELOG.md b/CHANGELOG.md
index e5ee5796..cfb1d672 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -56,6 +56,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Bug Fixes
 
+* (rpc) [tharsis#598](https://github.com/tharsis/ethermint/pull/598) Check truncation when creating a `BlockNumber` from `big.Int`
 * (evm) [tharsis#597](https://github.com/tharsis/ethermint/pull/597) Check for `uint64` -> `int64` block height overflow on `GetHashFn`
 * (evm) [tharsis#579](https://github.com/tharsis/ethermint/pull/579) Update `DeriveChainID` function to handle `v` signature values `< 35`.
 * (encoding) [tharsis#478](https://github.com/tharsis/ethermint/pull/478) Register `Evidence` to amino codec.
diff --git a/ethereum/rpc/types/block.go b/ethereum/rpc/types/block.go
index 96364f7f..f368951d 100644
--- a/ethereum/rpc/types/block.go
+++ b/ethereum/rpc/types/block.go
@@ -9,13 +9,15 @@ import (
 	"math/big"
 	"strings"
 
-	"github.com/ethereum/go-ethereum/common"
-
-	grpctypes "github.com/cosmos/cosmos-sdk/types/grpc"
 	"github.com/spf13/cast"
 	"google.golang.org/grpc/metadata"
 
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
+
+	grpctypes "github.com/cosmos/cosmos-sdk/types/grpc"
+
+	ethermint "github.com/tharsis/ethermint/types"
 )
 
 // BlockNumber represents decoding hex string to block values
@@ -35,6 +37,11 @@ const (
 
 // NewBlockNumber creates a new BlockNumber instance.
 func NewBlockNumber(n *big.Int) BlockNumber {
+	if !n.IsInt64() {
+		// default to latest block if it overflows
+		return EthLatestBlockNumber
+	}
+
 	return BlockNumber(n.Int64())
 }
 
@@ -176,10 +183,13 @@ func (bnh *BlockNumberOrHash) decodeFromString(input string) error {
 		if err != nil {
 			return err
 		}
-		if blockNumber > math.MaxInt64 {
-			return fmt.Errorf("blocknumber %d is too high", blockNumber)
+
+		bnInt, err := ethermint.SafeInt64(blockNumber)
+		if err != nil {
+			return err
 		}
-		bn := BlockNumber(blockNumber)
+
+		bn := BlockNumber(bnInt)
 		bnh.BlockNumber = &bn
 	}
 	return nil