diff --git a/core/blockchain.go b/core/blockchain.go
index cea24d9e66..ed89e2d15f 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -1158,7 +1158,7 @@ func (bc *BlockChain) Stop() {
 
 	// Signal shutdown to all goroutines.
 	close(bc.quit)
-	bc.StopInsert()
+	bc.InterruptInsert(true)
 
 	// Now wait for all chain modifications to end and persistent goroutines to exit.
 	//
@@ -1180,11 +1180,15 @@ func (bc *BlockChain) Stop() {
 	log.Info("Blockchain manager stopped")
 }
 
-// StopInsert interrupts all insertion methods, causing them to return
-// errInsertionInterrupted as soon as possible. Insertion is permanently disabled after
-// calling this method.
-func (bc *BlockChain) StopInsert() {
-	bc.procInterrupt.Store(true)
+// InterruptInsert interrupts all insertion methods, causing them to return
+// errInsertionInterrupted as soon as possible, or resume the chain insertion
+// if required.
+func (bc *BlockChain) InterruptInsert(on bool) {
+	if on {
+		bc.procInterrupt.Store(true)
+	} else {
+		bc.procInterrupt.Store(false)
+	}
 }
 
 // insertStopped returns true after StopInsert has been called.
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index a10bc96fff..3986e1833b 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -200,6 +200,9 @@ type BlockChain interface {
 	// InsertChain inserts a batch of blocks into the local chain.
 	InsertChain(types.Blocks) (int, error)
 
+	// InterruptInsert disables or enables chain insertion.
+	InterruptInsert(on bool)
+
 	// InsertReceiptChain inserts a batch of receipts into the local chain.
 	InsertReceiptChain(types.Blocks, []types.Receipts) (int, error)
 }
@@ -532,8 +535,10 @@ func (d *Downloader) cancel() {
 // Cancel aborts all of the operations and waits for all download goroutines to
 // finish before returning.
 func (d *Downloader) Cancel() {
+	d.blockchain.InterruptInsert(true)
 	d.cancel()
 	d.cancelWg.Wait()
+	d.blockchain.InterruptInsert(false)
 }
 
 // Terminate interrupts the downloader, canceling all pending operations.
diff --git a/eth/downloader/downloader_test.go b/eth/downloader/downloader_test.go
index 6d5cfbe50f..712f04d316 100644
--- a/eth/downloader/downloader_test.go
+++ b/eth/downloader/downloader_test.go
@@ -335,6 +335,9 @@ func (dl *downloadTester) Config() *params.ChainConfig {
 	return &config
 }
 
+func (bc *downloadTester) InterruptInsert(on bool) {
+}
+
 type downloadTesterPeer struct {
 	dl            *downloadTester
 	id            string
diff --git a/internal/ethapi/api.go b/internal/ethapi/api.go
index f4a66e1642..81a8946602 100644
--- a/internal/ethapi/api.go
+++ b/internal/ethapi/api.go
@@ -2445,8 +2445,16 @@ func (api *DebugAPI) ChaindbCompact() error {
 }
 
 // SetHead rewinds the head of the blockchain to a previous block.
-func (api *DebugAPI) SetHead(number hexutil.Uint64) {
+func (api *DebugAPI) SetHead(number hexutil.Uint64) error {
+	header := api.b.CurrentHeader()
+	if header == nil {
+		return errors.New("current header is not available")
+	}
+	if header.Number.Uint64() <= uint64(number) {
+		return errors.New("not allowed to rewind to a future block")
+	}
 	api.b.SetHead(uint64(number))
+	return nil
 }
 
 // DbGet returns the raw value of a key stored in the database.