diff --git a/modules/brother/cmd/brother/printlink_test.go b/modules/brother/cmd/brother/printlink_test.go
index 045c4eb8..56670d1f 100644
--- a/modules/brother/cmd/brother/printlink_test.go
+++ b/modules/brother/cmd/brother/printlink_test.go
@@ -6,12 +6,14 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 )
 
 // uploadFake stands for node-files.upload on another machine: it records the ask and answers a key, or refuses.
 type uploadFake struct {
+	mu    sync.Mutex
 	calls []string
 	key   string
 	err   error
@@ -19,11 +21,20 @@ type uploadFake struct {
 
 // withUpload puts a fake node-files in the tool side's place, and the bucket file the mesh writes from the binding
 // (files/bucket.json) where the tool reads it.
+// seen is the uploads asked so far, read under the fake's lock (the print runs in the background).
+func (f *uploadFake) seen() []string {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]string(nil), f.calls...)
+}
+
 func withUpload(t *testing.T, key string, err error) *uploadFake {
 	t.Helper()
 	f := &uploadFake{key: key, err: err}
 	old := uploadVia
 	uploadVia = func(node, path, bucket string) (string, error) {
+		f.mu.Lock()
+		defer f.mu.Unlock()
 		f.calls = append(f.calls, node+"|"+path+"|"+bucket)
 		return f.key, f.err
 	}
@@ -66,8 +77,8 @@ func TestPrintTakesExactlyOneSource(t *testing.T) {
 			t.Errorf("%s: the refusal does not name the rule: %v", name, err)
 		}
 	}
-	if r.bus.asks() != 0 || len(up.calls) != 0 || fake.body != nil {
-		t.Errorf("%d asks queued, %d uploads asked, printer sent %d bytes", r.bus.asks(), len(up.calls), len(fake.body))
+	if r.bus.asks() != 0 || len(up.seen()) != 0 || fake.body != nil {
+		t.Errorf("%d asks queued, %d uploads asked, printer sent %d bytes", r.bus.asks(), len(up.seen()), len(fake.body))
 	}
 }
 
@@ -84,8 +95,8 @@ func TestPrintOfAFileOfAnotherMachineUploadsThenPrintsTheKey(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if len(up.calls) != 1 || up.calls[0] != "g14|/home/ops/letter.pdf|brother-test" {
-		t.Fatalf("uploads asked: %v", up.calls)
+	if len(up.seen()) != 1 || up.seen()[0] != "g14|/home/ops/letter.pdf|brother-test" {
+		t.Fatalf("uploads asked: %v", up.seen())
 	}
 	if len(r.bus.published) != 1 {
 		t.Fatalf("%d asks queued", len(r.bus.published))
@@ -120,8 +131,8 @@ func TestARefusedUploadIsAnsweredWithItsReasonAndNothingIsPrinted(t *testing.T)
 	if err == nil || !strings.Contains(err.Error(), "is refused by name: it is in .ssh") {
 		t.Fatalf("error = %v", err)
 	}
-	if len(up.calls) != 1 || r.bus.asks() != 0 || fake.body != nil {
-		t.Errorf("%d uploads, %d asks queued, printer sent %d bytes", len(up.calls), r.bus.asks(), len(fake.body))
+	if len(up.seen()) != 1 || r.bus.asks() != 0 || fake.body != nil {
+		t.Errorf("%d uploads, %d asks queued, printer sent %d bytes", len(up.seen()), r.bus.asks(), len(fake.body))
 	}
 }
 
@@ -272,7 +283,7 @@ func TestASlowUploadAndPrintAnswersStartedNeverATimeout(t *testing.T) {
 	}
 	m := got.(map[string]any)
 	id, _ := m["ask"].(string)
-	if m["state"] != "started" || id == "" || len(up.calls) > 1 {
+	if m["state"] != "started" || id == "" || len(up.seen()) > 1 {
 		t.Fatalf("answer %v", m)
 	}
 	for deadline := time.Now().Add(5 * time.Second); ; {
@@ -290,8 +301,8 @@ func TestASlowUploadAndPrintAnswersStartedNeverATimeout(t *testing.T) {
 			t.Fatal("never done")
 		}
 	}
-	if len(up.calls) != 1 || len(r.bus.published) != 1 || r.bus.published[0].Object != key {
-		t.Errorf("uploads %v, asks %v", up.calls, r.bus.published)
+	if len(up.seen()) != 1 || len(r.bus.published) != 1 || r.bus.published[0].Object != key {
+		t.Errorf("uploads %v, asks %v", up.seen(), r.bus.published)
 	}
 	// An upload that fails after the call answered is the outcome, read with the ask.
 	uploadVia = func(node, path, bucket string) (string, error) {