diff --git a/pcbnew/zone.cpp b/pcbnew/zone.cpp
index e850f9f456..fe642aaa48 100644
--- a/pcbnew/zone.cpp
+++ b/pcbnew/zone.cpp
@@ -344,14 +344,13 @@ const BOX2I ZONE::GetBoundingBox() const
     if( const BOARD* board = GetBoard() )
     {
         std::unordered_map<const ZONE*, BOX2I>& cache = board->m_ZoneBBoxCache;
+        std::unique_lock<std::mutex>            cacheLock( const_cast<BOARD*>( board )->m_CachesMutex );
         auto                                    cacheIter = cache.find( this );
 
         if( cacheIter != cache.end() )
             return cacheIter->second;
 
         BOX2I bbox = m_Poly->BBox();
-
-        std::unique_lock<std::mutex> cacheLock( const_cast<BOARD*>( board )->m_CachesMutex );
         cache[ this ] = bbox;
 
         return bbox;
@@ -365,12 +364,11 @@ void ZONE::CacheBoundingBox()
 {
     BOARD*                                  board = GetBoard();
     std::unordered_map<const ZONE*, BOX2I>& cache = board->m_ZoneBBoxCache;
-
-    auto cacheIter = cache.find( this );
+    std::unique_lock<std::mutex>            cacheLock( board->m_CachesMutex );
+    auto                                    cacheIter = cache.find( this );
 
     if( cacheIter == cache.end() )
     {
-        std::unique_lock<std::mutex> cacheLock( board->m_CachesMutex );
         cache[ this ] = m_Poly->BBox();
     }
 }