diff --git a/components/lazmapviewer/source/mvmapviewer.pas b/components/lazmapviewer/source/mvmapviewer.pas
index 52095370f..4a7858c2b 100644
--- a/components/lazmapviewer/source/mvmapviewer.pas
+++ b/components/lazmapviewer/source/mvmapviewer.pas
@@ -616,8 +616,11 @@ var
   trkColor: TColor;
   trkWidth: Integer;
 begin
-  if trk.Visible and (trk.Points.Count > 0) then
-  begin
+  if not trk.Visible or (trk.Points.Count = 0) then
+    exit;
+
+  GPSItems.Lock;
+  try
     // Determine track color
     if trk.LineColor = clDefault then
     begin
@@ -657,6 +660,8 @@ begin
         LastInside := IsInside;
       end;
     end;
+  finally
+    GPSItems.Unlock;
   end;
 end;