diff --git a/pcbnew/drc/drc_rtree.h b/pcbnew/drc/drc_rtree.h
index 2365d90bed..2e8867dec1 100644
--- a/pcbnew/drc/drc_rtree.h
+++ b/pcbnew/drc/drc_rtree.h
@@ -92,6 +92,7 @@ public:
                 [&]( PCB_LAYER_ID layer )
                 {
                     std::shared_ptr<SHAPE> shape = aItem->GetEffectiveShape( layer );
+                    subshapes.clear();
 
                     if( shape->HasIndexableSubshapes() )
                         shape->GetIndexableSubshapes( subshapes );