diff --git a/core/error.go b/core/error.go
index 11d8c1653..6af48ac2d 100644
--- a/core/error.go
+++ b/core/error.go
@@ -1,10 +1,16 @@
 package core
 
 import (
+	"errors"
 	"fmt"
 	"math/big"
 )
 
+var (
+	BlockNumberErr = errors.New("block number invalid")
+	BlockFutureErr = errors.New("block time is in the future")
+)
+
 // Parent error. In case a parent is unknown this error will be thrown
 // by the block manager
 type ParentErr struct {