diff --git a/eth/downloader/beaconsync.go b/eth/downloader/beaconsync.go
index 2905b664ed..16124d1d70 100644
--- a/eth/downloader/beaconsync.go
+++ b/eth/downloader/beaconsync.go
@@ -306,9 +306,13 @@ func (d *Downloader) fetchHeaders(from uint64) error {
 		// If the pivot became stale (older than 2*64-8 (bit of wiggle room)),
 		// move it ahead to HEAD-64.
 		//
+		// Note the pivot is only moved before its commitment. Once the pivot
+		// is committed, the chain obtains a stateful head and pivot block should
+		// be on longer advanced.
+		//
 		// The state syncer is consulted first before the pivot movement.
 		d.pivotLock.Lock()
-		if d.pivotHeader != nil && d.snapSyncer.FrozenPivot() == nil {
+		if d.pivotHeader != nil && !d.committed.Load() && d.snapSyncer.FrozenPivot() == nil {
 			if head.Number.Uint64() > d.pivotHeader.Number.Uint64()+2*uint64(fsMinFullBlocks)-8 {
 				// Retrieve the next pivot header, either from skeleton chain
 				// or the filled chain
diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 876115ea97..e99de20701 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -387,9 +387,13 @@ func (d *Downloader) synchronise(beaconPing chan struct{}) (err error) {
 	// Obtain the synchronized used in this cycle
 	mode := d.moder.get(true)
 	defer func() {
+		// The snap-sync mode is usually already disabled right after the pivot
+		// commitment; this is the fallback for the cycles terminating without
+		// a pivot block (e.g. a short chain fully imported from genesis).
 		if err == nil && mode == ethconfig.SnapSync {
-			d.moder.disableSnap()
-			log.Info("Disabled snap-sync after the initial sync cycle")
+			if d.moder.disableSnap() {
+				log.Info("Disabled snap-sync after the initial sync cycle")
+			}
 		}
 	}()
 
@@ -1106,6 +1110,13 @@ func (d *Downloader) commitPivotBlock(result *fetchResult) error {
 		return err
 	}
 	d.committed.Store(true)
+
+	// The chain has obtained a stateful head by committing the pivot block,
+	// the mission of the snap sync is regarded as accomplished and the mode
+	// is flipped to full-sync.
+	if d.moder.disableSnap() {
+		log.Info("Disabled snap-sync after pivot commitment", "number", block.Number(), "hash", block.Hash())
+	}
 	return nil
 }
 
diff --git a/eth/downloader/syncmode.go b/eth/downloader/syncmode.go
index a7792eb5fc..5cbf06bedf 100644
--- a/eth/downloader/syncmode.go
+++ b/eth/downloader/syncmode.go
@@ -107,9 +107,15 @@ func (m *syncModer) get(report bool) ethconfig.SyncMode {
 	return ethconfig.FullSync
 }
 
-// disableSnap disables the snap sync mode, usually it's called after a successful snap sync.
-func (m *syncModer) disableSnap() {
+// disableSnap disables the snap sync mode and reports whether the mode was
+// actually flipped.
+func (m *syncModer) disableSnap() bool {
 	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	if m.mode == ethconfig.FullSync {
+		return false
+	}
 	m.mode = ethconfig.FullSync
-	m.lock.Unlock()
+	return true
 }