diff --git a/cmd/geth/admin.go b/cmd/geth/admin.go
index 28786553c..8f9a009d7 100644
--- a/cmd/geth/admin.go
+++ b/cmd/geth/admin.go
@@ -88,6 +88,7 @@ func (js *jsre) adminBindings() {
 	debug.Set("getBlockRlp", js.getBlockRlp)
 	debug.Set("setHead", js.setHead)
 	debug.Set("processBlock", js.debugBlock)
+	debug.Set("seedhash", js.seedHash)
 	// undocumented temporary
 	debug.Set("waitForBlocks", js.waitForBlocks)
 }
@@ -118,6 +119,27 @@ func (js *jsre) getBlock(call otto.FunctionCall) (*types.Block, error) {
 	return block, nil
 }
 
+func (js *jsre) seedHash(call otto.FunctionCall) otto.Value {
+	if len(call.ArgumentList) > 0 {
+		if call.Argument(0).IsNumber() {
+			num, _ := call.Argument(0).ToInteger()
+			hash, err := ethash.GetSeedHash(uint64(num))
+			if err != nil {
+				fmt.Println(err)
+				return otto.UndefinedValue()
+			}
+			v, _ := call.Otto.ToValue(fmt.Sprintf("0x%x", hash))
+			return v
+		} else {
+			fmt.Println("arg not a number")
+		}
+	} else {
+		fmt.Println("requires number argument")
+	}
+
+	return otto.UndefinedValue()
+}
+
 func (js *jsre) pendingTransactions(call otto.FunctionCall) otto.Value {
 	txs := js.ethereum.TxPool().GetTransactions()
 
@@ -220,10 +242,11 @@ func (js *jsre) debugBlock(call otto.FunctionCall) otto.Value {
 	vm.Debug = true
 	_, err = js.ethereum.BlockProcessor().RetryProcess(block)
 	if err != nil {
-		glog.Infoln(err)
+		fmt.Println(err)
 	}
 	vm.Debug = old
 
+	fmt.Println("ok")
 	return otto.UndefinedValue()
 }
 
diff --git a/core/block_processor.go b/core/block_processor.go
index 3f10e5efd..037782407 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -21,7 +21,7 @@ import (
 const (
 	// must be bumped when consensus algorithm is changed, this forces the upgradedb
 	// command to be run (forces the blocks to be imported again using the new algorithm)
-	BlockChainVersion = 2
+	BlockChainVersion = 3
 )
 
 var receiptsPre = []byte("receipts-")
@@ -159,6 +159,9 @@ func (sm *BlockProcessor) RetryProcess(block *types.Block) (logs state.Logs, err
 		return nil, ParentError(header.ParentHash)
 	}
 	parent := sm.bc.GetBlock(header.ParentHash)
+	if !sm.Pow.Verify(block) {
+		return nil, ValidationError("Block's nonce is invalid (= %x)", block.Nonce)
+	}
 
 	return sm.processWithParent(block, parent)
 }