diff --git a/ipn/ipnlocal/serve_test.go b/ipn/ipnlocal/serve_test.go
index a09729d78..626615484 100644
--- a/ipn/ipnlocal/serve_test.go
+++ b/ipn/ipnlocal/serve_test.go
@@ -29,6 +29,7 @@
 	"tailscale.com/ipn/store/mem"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tsd"
+	"tailscale.com/tstest"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
 	"tailscale.com/types/netmap"
@@ -668,7 +669,7 @@ func newTestBackend(t *testing.T) *LocalBackend {
 	var logf logger.Logf = logger.Discard
 	const debug = true
 	if debug {
-		logf = logger.WithPrefix(t.Logf, "... ")
+		logf = logger.WithPrefix(tstest.WhileTestRunningLogger(t), "... ")
 	}
 
 	sys := &tsd.System{}