diff --git a/libs/kimath/src/geometry/shape_poly_set.cpp b/libs/kimath/src/geometry/shape_poly_set.cpp
index 6df5657f04..0fe60b07e5 100644
--- a/libs/kimath/src/geometry/shape_poly_set.cpp
+++ b/libs/kimath/src/geometry/shape_poly_set.cpp
@@ -1623,6 +1623,9 @@ void SHAPE_POLY_SET::Mirror( bool aX, bool aY, const VECTOR2I& aRef )
         for( SHAPE_LINE_CHAIN& path : poly )
             path.Mirror( aX, aY, aRef );
     }
+
+    if( m_triangulationValid )
+        CacheTriangulation();
 }