diff --git a/lib/scanner/blockqueue.go b/lib/scanner/blockqueue.go
index a7763403..1ab720ce 100644
--- a/lib/scanner/blockqueue.go
+++ b/lib/scanner/blockqueue.go
@@ -19,7 +19,7 @@ import (
 // workers are used in parallel. The outbox will become closed when the inbox
 // is closed and all items handled.
 
-func newParallelHasher(dir string, blockSize, workers int, outbox, inbox chan protocol.FileInfo, counter *uint64, done chan struct{}) {
+func newParallelHasher(dir string, blockSize, workers int, outbox, inbox chan protocol.FileInfo, counter *int64, done chan struct{}) {
 	wg := sync.NewWaitGroup()
 	wg.Add(workers)
 
@@ -39,7 +39,7 @@ func newParallelHasher(dir string, blockSize, workers int, outbox, inbox chan pr
 	}()
 }
 
-func HashFile(path string, blockSize int, sizeHint int64, counter *uint64) ([]protocol.BlockInfo, error) {
+func HashFile(path string, blockSize int, sizeHint int64, counter *int64) ([]protocol.BlockInfo, error) {
 	fd, err := os.Open(path)
 	if err != nil {
 		if debug {
@@ -63,7 +63,7 @@ func HashFile(path string, blockSize int, sizeHint int64, counter *uint64) ([]pr
 	return Blocks(fd, blockSize, sizeHint, counter)
 }
 
-func hashFiles(dir string, blockSize int, outbox, inbox chan protocol.FileInfo, counter *uint64) {
+func hashFiles(dir string, blockSize int, outbox, inbox chan protocol.FileInfo, counter *int64) {
 	for f := range inbox {
 		if f.IsDirectory() || f.IsDeleted() {
 			panic("Bug. Asked to hash a directory or a deleted file.")
diff --git a/lib/scanner/blocks.go b/lib/scanner/blocks.go
index b853b2aa..06178b11 100644
--- a/lib/scanner/blocks.go
+++ b/lib/scanner/blocks.go
@@ -19,7 +19,7 @@ import (
 var SHA256OfNothing = []uint8{0xe3, 0xb0, 0xc4, 0x42, 0x98, 0xfc, 0x1c, 0x14, 0x9a, 0xfb, 0xf4, 0xc8, 0x99, 0x6f, 0xb9, 0x24, 0x27, 0xae, 0x41, 0xe4, 0x64, 0x9b, 0x93, 0x4c, 0xa4, 0x95, 0x99, 0x1b, 0x78, 0x52, 0xb8, 0x55}
 
 // Blocks returns the blockwise hash of the reader.
-func Blocks(r io.Reader, blocksize int, sizehint int64, counter *uint64) ([]protocol.BlockInfo, error) {
+func Blocks(r io.Reader, blocksize int, sizehint int64, counter *int64) ([]protocol.BlockInfo, error) {
 	var blocks []protocol.BlockInfo
 	if sizehint > 0 {
 		blocks = make([]protocol.BlockInfo, 0, int(sizehint/int64(blocksize)))
@@ -38,7 +38,7 @@ func Blocks(r io.Reader, blocksize int, sizehint int64, counter *uint64) ([]prot
 		}
 
 		if counter != nil {
-			atomic.AddUint64(counter, uint64(n))
+			atomic.AddInt64(counter, int64(n))
 		}
 
 		b := protocol.BlockInfo{
diff --git a/lib/scanner/walk.go b/lib/scanner/walk.go
index a4079b5f..869c944d 100644
--- a/lib/scanner/walk.go
+++ b/lib/scanner/walk.go
@@ -139,10 +139,10 @@ func (w *Walker) Walk() (chan protocol.FileInfo, error) {
 	// which it receives the files we ask it to hash.
 	go func() {
 		var filesToHash []protocol.FileInfo
-		var total, progress uint64
+		var total, progress int64
 		for file := range toHashChan {
 			filesToHash = append(filesToHash, file)
-			total += uint64(file.CachedSize)
+			total += int64(file.CachedSize)
 		}
 
 		realToHashChan := make(chan protocol.FileInfo)
@@ -161,7 +161,7 @@ func (w *Walker) Walk() (chan protocol.FileInfo, error) {
 					ticker.Stop()
 					return
 				case <-ticker.C:
-					current := atomic.LoadUint64(&progress)
+					current := atomic.LoadInt64(&progress)
 					if debug {
 						l.Debugf("Walk %s %s current progress %d/%d (%d%%)", w.Dir, w.Subs, current, total, current*100/total)
 					}