diff --git a/pkg/checksum/checker.go b/pkg/checksum/checker.go
index 790b336..c74e8f1 100644
--- a/pkg/checksum/checker.go
+++ b/pkg/checksum/checker.go
@@ -25,23 +25,23 @@ import (
 
 type Checker struct {
 	sync.Mutex
-	table                  *table.TableInfo
-	newTable               *table.TableInfo
-	concurrency            int
-	feed                   *repl.Client
-	db                     *sql.DB
-	trxPool                *dbconn.TrxPool
-	isInvalid              bool
-	chunker                table.Chunker
-	startTime              time.Time
-	ExecTime               time.Duration
-	recentValue            interface{} // used for status
-	dbConfig               *dbconn.DBConfig
-	logger                 loggers.Advanced
-	fixDifferences         bool
-	differencesFound       atomic.Uint64
-	recopyLock             sync.Mutex
-	isResumeFromCheckpoint bool
+	table            *table.TableInfo
+	newTable         *table.TableInfo
+	concurrency      int
+	feed             *repl.Client
+	db               *sql.DB
+	trxPool          *dbconn.TrxPool
+	isInvalid        bool
+	chunker          table.Chunker
+	startTime        time.Time
+	ExecTime         time.Duration
+	recentValue      interface{} // used for status
+	dbConfig         *dbconn.DBConfig
+	logger           loggers.Advanced
+	fixDifferences   bool
+	differencesFound atomic.Uint64
+	recopyLock       sync.Mutex
+	isResume         bool
 }
 
 type CheckerConfig struct {
@@ -87,16 +87,16 @@ func NewChecker(db *sql.DB, tbl, newTable *table.TableInfo, feed *repl.Client, c
 		}
 	}
 	checksum := &Checker{
-		table:                  tbl,
-		newTable:               newTable,
-		concurrency:            config.Concurrency,
-		db:                     db,
-		feed:                   feed,
-		chunker:                chunker,
-		dbConfig:               config.DBConfig,
-		logger:                 config.Logger,
-		fixDifferences:         config.FixDifferences,
-		isResumeFromCheckpoint: config.Watermark != "",
+		table:          tbl,
+		newTable:       newTable,
+		concurrency:    config.Concurrency,
+		db:             db,
+		feed:           feed,
+		chunker:        chunker,
+		dbConfig:       config.DBConfig,
+		logger:         config.Logger,
+		fixDifferences: config.FixDifferences,
+		isResume:       config.Watermark != "",
 	}
 	return checksum, nil
 }
@@ -170,6 +170,9 @@ func (c *Checker) RecentValue() string {
 }
 
 func (c *Checker) GetLowWatermark() (string, error) {
+	if c.chunker == nil {
+		return "", errors.New("chunker not initialized")
+	}
 	return c.chunker.GetLowWatermark()
 }
 
@@ -380,7 +383,7 @@ func (c *Checker) Run(ctx context.Context) error {
 	// Open the chunker if it's not open.
 	// It will already be open if this is a resume from checkpoint.
 	// This is a little annoying, but just the way the chunker API works.
-	if !c.isResumeFromCheckpoint {
+	if !c.isResume {
 		if err := c.chunker.Open(); err != nil {
 			return err
 		}
diff --git a/pkg/checksum/checker_test.go b/pkg/checksum/checker_test.go
index 76f5d91..abeca61 100644
--- a/pkg/checksum/checker_test.go
+++ b/pkg/checksum/checker_test.go
@@ -258,3 +258,36 @@ func TestChangeDataTypeDatetime(t *testing.T) {
 	assert.NoError(t, err)
 	assert.NoError(t, checker.Run(context.Background())) // fails
 }
+
+func TestFromWatermark(t *testing.T) {
+	testutils.RunSQL(t, "DROP TABLE IF EXISTS tfromwatermark, _tfromwatermark_new, _tfromwatermark_chkpnt")
+	testutils.RunSQL(t, "CREATE TABLE tfromwatermark (a INT NOT NULL, b INT, c INT, PRIMARY KEY (a))")
+	testutils.RunSQL(t, "CREATE TABLE _tfromwatermark_new (a INT NOT NULL, b INT, c INT, PRIMARY KEY (a))")
+	testutils.RunSQL(t, "CREATE TABLE _tfromwatermark_chkpnt (a INT)") // for binlog advancement
+	testutils.RunSQL(t, "INSERT INTO tfromwatermark VALUES (1, 2, 3)")
+	testutils.RunSQL(t, "INSERT INTO _tfromwatermark_new VALUES (1, 2, 3)")
+
+	db, err := dbconn.New(testutils.DSN(), dbconn.NewDBConfig())
+	assert.NoError(t, err)
+
+	t1 := table.NewTableInfo(db, "test", "tfromwatermark")
+	assert.NoError(t, t1.SetInfo(context.TODO()))
+	t2 := table.NewTableInfo(db, "test", "_tfromwatermark_new")
+	assert.NoError(t, t2.SetInfo(context.TODO()))
+	logger := logrus.New()
+
+	cfg, err := mysql.ParseDSN(testutils.DSN())
+	assert.NoError(t, err)
+	feed := repl.NewClient(db, cfg.Addr, t1, t2, cfg.User, cfg.Passwd, &repl.ClientConfig{
+		Logger:          logger,
+		Concurrency:     4,
+		TargetBatchTime: time.Second,
+	})
+	assert.NoError(t, feed.Run())
+
+	config := NewCheckerDefaultConfig()
+	config.Watermark = "{\"Key\":[\"a\"],\"ChunkSize\":1000,\"LowerBound\":{\"Value\": [\"2\"],\"Inclusive\":true},\"UpperBound\":{\"Value\": [\"3\"],\"Inclusive\":false}}"
+	checker, err := NewChecker(db, t1, t2, feed, config)
+	assert.NoError(t, err)
+	assert.NoError(t, checker.Run(context.Background()))
+}
diff --git a/pkg/migration/runner.go b/pkg/migration/runner.go
index 58dbf84..a2aa473 100644
--- a/pkg/migration/runner.go
+++ b/pkg/migration/runner.go
@@ -42,7 +42,7 @@ const (
 
 // These are really consts, but set to var for testing.
 var (
-	checkpointDumpInterval  = 2 * time.Second
+	checkpointDumpInterval  = 50 * time.Second
 	tableStatUpdateInterval = 5 * time.Minute
 	statusInterval          = 30 * time.Second
 	sentinelCheckInterval   = 1 * time.Second
@@ -917,10 +917,12 @@ func (r *Runner) dumpCheckpoint(ctx context.Context) error {
 	var checksumWatermark string
 	if r.getCurrentState() >= stateChecksum {
 		r.checkerLock.Lock()
-		checksumWatermark, err = r.checker.GetLowWatermark()
-		r.checkerLock.Unlock()
-		if err != nil {
-			return err
+		defer r.checkerLock.Unlock()
+		if r.checker != nil {
+			checksumWatermark, err = r.checker.GetLowWatermark()
+			if err != nil {
+				return err
+			}
 		}
 	}
 	copyRows := atomic.LoadUint64(&r.copier.CopyRowsCount)
diff --git a/pkg/migration/runner_test.go b/pkg/migration/runner_test.go
index ca98c49..6028c83 100644
--- a/pkg/migration/runner_test.go
+++ b/pkg/migration/runner_test.go
@@ -955,6 +955,77 @@ func TestCheckpointRestore(t *testing.T) {
 	assert.True(t, r2.usedResumeFromCheckpoint)
 }
 
+func TestCheckpointResumeDuringChecksum(t *testing.T) {
+	tbl := `CREATE TABLE cptresume (
+		id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
+		id2 INT NOT NULL,
+		pad VARCHAR(100) NOT NULL default 0)`
+	cfg, err := mysql.ParseDSN(testutils.DSN())
+	assert.NoError(t, err)
+	testutils.RunSQL(t, `DROP TABLE IF EXISTS cptresume, _cptresume_new, _cptresume_chkpnt, _cptresume_sentinel`)
+	testutils.RunSQL(t, tbl)
+	testutils.RunSQL(t, `CREATE TABLE _cptresume_sentinel (id INT NOT NULL PRIMARY KEY)`)
+	testutils.RunSQL(t, `insert into cptresume (id2,pad) SELECT 1, REPEAT('a', 100) FROM dual`)
+	testutils.RunSQL(t, `insert into cptresume (id2,pad) SELECT 1, REPEAT('a', 100) FROM cptresume`)
+	testutils.RunSQL(t, `insert into cptresume (id2,pad) SELECT 1, REPEAT('a', 100) FROM cptresume a JOIN cptresume b JOIN cptresume c`)
+
+	r, err := NewRunner(&Migration{
+		Host:            cfg.Addr,
+		Username:        cfg.User,
+		Password:        cfg.Passwd,
+		Database:        cfg.DBName,
+		Threads:         4,
+		TargetChunkTime: 100 * time.Millisecond,
+		Table:           "cptresume",
+		Alter:           "ENGINE=InnoDB",
+		Checksum:        true,
+	})
+	assert.NoError(t, err)
+
+	// Call r.Run() with our context in a go-routine.
+	// When we see that we are waiting on the sentinel table,
+	// we then manually start the first bits of checksum, and then close()
+	// We should be able to resume from the checkpoint into the checksum state.
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		err := r.Run(ctx)
+		assert.Error(t, err)
+	}()
+	for {
+		// Wait for the sentinel table.
+		if r.getCurrentState() >= stateWaitingOnSentinelTable {
+			break
+		}
+		time.Sleep(time.Millisecond)
+	}
+
+	assert.NoError(t, r.checksum(context.TODO()))       // run the checksum, the original Run is blocked on sentinel.
+	assert.NoError(t, r.dumpCheckpoint(context.TODO())) // dump a checkpoint with the watermark.
+	cancel()                                            // unblock the original waiting on sentinel.
+	assert.NoError(t, r.Close())                        // close the run.
+
+	// drop the sentinel table.
+	testutils.RunSQL(t, `DROP TABLE _cptresume_sentinel`)
+
+	// Start again as a new runner,
+	r2, err := NewRunner(&Migration{
+		Host:            cfg.Addr,
+		Username:        cfg.User,
+		Password:        cfg.Passwd,
+		Database:        cfg.DBName,
+		Threads:         4,
+		TargetChunkTime: 100 * time.Millisecond,
+		Table:           "cptresume",
+		Alter:           "ENGINE=InnoDB",
+		Checksum:        true,
+	})
+	assert.NoError(t, err)
+	err = r2.Run(context.Background())
+	assert.NoError(t, err)
+	assert.True(t, r2.usedResumeFromCheckpoint)
+	assert.NotEmpty(t, r2.checksumWatermark) // it had a checksum watermark
+}
+
 func TestCheckpointDifferentRestoreOptions(t *testing.T) {
 	tbl := `CREATE TABLE cpt1difft1 (
 		id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
@@ -2674,7 +2745,7 @@ func TestResumeFromCheckpointE2EWithManualSentinel(t *testing.T) {
 
 	go func() {
 		err := runner.Run(ctx)
-		assert.ErrorContains(t, err, "context canceled") // it gets interrupted as soon as there is a checkpoint saved.
+		assert.Error(t, err) // it gets interrupted as soon as there is a checkpoint saved.
 	}()
 
 	// wait until a checkpoint is saved (which means copy is in progress)