diff --git a/cmd/syncthing/main.go b/cmd/syncthing/main.go
index c34156d70..8b29fdc0d 100644
--- a/cmd/syncthing/main.go
+++ b/cmd/syncthing/main.go
@@ -1054,7 +1054,7 @@ func (m migratingAPI) Serve(ctx context.Context) error {
 	srv := &http.Server{
 		Addr: m.addr,
 		Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			w.Header().Set("Content-Type", "text/plain")
+			w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 			w.Write([]byte("*** Database migration in progress ***\n\n"))
 			for _, line := range slogutil.GlobalRecorder.Since(time.Time{}) {
 				_, _ = line.WriteTo(w, slogutil.DefaultLineFormat)
diff --git a/lib/pmp/debug.go b/lib/pmp/debug.go
index 3a76691c5..a1cee6938 100644
--- a/lib/pmp/debug.go
+++ b/lib/pmp/debug.go
@@ -8,4 +8,4 @@ package pmp
 
 import "github.com/syncthing/syncthing/internal/slogutil"
 
-var l = slogutil.NewAdapter("NAT-PMP discovery and port mapping")
+func init() { slogutil.RegisterPackage("NAT-PMP discovery and port mapping") }
diff --git a/lib/pmp/pmp.go b/lib/pmp/pmp.go
index 3b7ad8d46..035896fdd 100644
--- a/lib/pmp/pmp.go
+++ b/lib/pmp/pmp.go
@@ -16,6 +16,7 @@ import (
 
 	natpmp "github.com/jackpal/go-nat-pmp"
 
+	"github.com/syncthing/syncthing/internal/slogutil"
 	"github.com/syncthing/syncthing/lib/nat"
 	"github.com/syncthing/syncthing/lib/netutil"
 	"github.com/syncthing/syncthing/lib/osutil"
@@ -34,14 +35,14 @@ func Discover(ctx context.Context, renewal, timeout time.Duration) []nat.Device
 		return err
 	})
 	if err != nil {
-		l.Debugln("Failed to discover gateway", err)
+		slog.DebugContext(ctx, "Failed to discover gateway", slogutil.Error(err))
 		return nil
 	}
 	if ip == nil || ip.IsUnspecified() {
 		return nil
 	}
 
-	l.Debugln("Discovered gateway at", ip)
+	slog.DebugContext(ctx, "Discovered gateway", "ip", ip)
 
 	c := natpmp.NewClientWithTimeout(ip, timeout)
 	// Try contacting the gateway, if it does not respond, assume it does not
@@ -51,13 +52,8 @@ func Discover(ctx context.Context, renewal, timeout time.Duration) []nat.Device
 		return ierr
 	})
 	if err != nil {
-		if errors.Is(err, context.Canceled) {
-			return nil
-		}
-		if strings.Contains(err.Error(), "Timed out") {
-			slog.Debug("Timeout trying to get external address, assume no NAT-PMP available")
-			return nil
-		}
+		slog.DebugContext(ctx, "Failed to get external address", slogutil.Error(err))
+		return nil
 	}
 
 	var localIP net.IP
@@ -69,7 +65,7 @@ func Discover(ctx context.Context, renewal, timeout time.Duration) []nat.Device
 		conn.Close()
 		localIP, err = osutil.IPFromAddr(conn.LocalAddr())
 		if localIP == nil {
-			l.Debugln("Failed to lookup local IP", err)
+			slog.DebugContext(ctx, "Failed to lookup local IP", slogutil.Error(err))
 		}
 	}
 
diff --git a/lib/upgrade/upgrade_supported.go b/lib/upgrade/upgrade_supported.go
index d64dd3b10..fc236af52 100644
--- a/lib/upgrade/upgrade_supported.go
+++ b/lib/upgrade/upgrade_supported.go
@@ -101,6 +101,7 @@ func FetchLatestReleases(releasesURL, current string) []Release {
 		slog.Warn("Failed to fetch latest release information", slogutil.Error(err))
 		return nil
 	}
+	defer resp.Body.Close()
 	if resp.StatusCode > 299 {
 		slog.Warn("Failed to fetch latest release information", slogutil.Error(resp.Status))
 		return nil
@@ -111,7 +112,6 @@ func FetchLatestReleases(releasesURL, current string) []Release {
 	if err != nil {
 		slog.Warn("Failed to decode latest release information", slogutil.Error(err))
 	}
-	resp.Body.Close()
 
 	return rels
 }