diff --git a/src/core/geometry/qgscurvepolygon.cpp b/src/core/geometry/qgscurvepolygon.cpp
index f313be4cf523..000fda5f0712 100644
--- a/src/core/geometry/qgscurvepolygon.cpp
+++ b/src/core/geometry/qgscurvepolygon.cpp
@@ -80,11 +80,11 @@ QgsCurvePolygon::QgsCurvePolygon( const QgsCurvePolygon &p )
   mValidityFailureReason = p.mValidityFailureReason;
 }
 
+// cppcheck-suppress operatorEqVarError
 QgsCurvePolygon &QgsCurvePolygon::operator=( const QgsCurvePolygon &p )
 {
   if ( &p != this )
   {
-    clearCache();
     QgsSurface::operator=( p );
     if ( p.mExteriorRing )
     {
diff --git a/tests/src/core/geometry/testqgscurvepolygon.cpp b/tests/src/core/geometry/testqgscurvepolygon.cpp
index 36f160c326ae..58cf00763e1e 100644
--- a/tests/src/core/geometry/testqgscurvepolygon.cpp
+++ b/tests/src/core/geometry/testqgscurvepolygon.cpp
@@ -150,22 +150,37 @@ void TestQgsCurvePolygon::testCopyConstructor()
   QgsCurvePolygon poly2( poly1 );
   QCOMPARE( poly1, poly2 );
 
-  QgsCircularString *ext = new QgsCircularString();
-  ext->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZM, 0, 0, 1, 5 )
-                  << QgsPoint( Qgis::WkbType::PointZM, 0, 10, 2, 6 ) << QgsPoint( Qgis::WkbType::PointZM, 10, 10, 3, 7 )
-                  << QgsPoint( Qgis::WkbType::PointZM, 10, 0, 4, 8 ) << QgsPoint( Qgis::WkbType::PointZM, 0, 0, 1, 9 ) );
-  poly1.setExteriorRing( ext );
-
-  QgsCircularString *ring = new QgsCircularString();
-  ring->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZM, 1, 1, 1, 2 )
-                   << QgsPoint( Qgis::WkbType::PointZM, 1, 9, 2, 3 ) << QgsPoint( Qgis::WkbType::PointZM, 9, 9, 3, 6 )
-                   << QgsPoint( Qgis::WkbType::PointZM, 9, 1, 4, 4 ) << QgsPoint( Qgis::WkbType::PointZM, 1, 1, 1, 7 ) );
-  poly1.addInteriorRing( ring );
+  QgsCircularString *ext1 = new QgsCircularString();
+  ext1->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZM, 0, 0, 1, 5 )
+                   << QgsPoint( Qgis::WkbType::PointZM, 0, 10, 2, 6 ) << QgsPoint( Qgis::WkbType::PointZM, 10, 10, 3, 7 )
+                   << QgsPoint( Qgis::WkbType::PointZM, 10, 0, 4, 8 ) << QgsPoint( Qgis::WkbType::PointZM, 0, 0, 1, 9 ) );
+  poly1.setExteriorRing( ext1 );
+
+  QgsCircularString *ring1 = new QgsCircularString();
+  ring1->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZM, 1, 1, 1, 2 )
+                    << QgsPoint( Qgis::WkbType::PointZM, 1, 9, 2, 3 ) << QgsPoint( Qgis::WkbType::PointZM, 9, 9, 3, 6 )
+                    << QgsPoint( Qgis::WkbType::PointZM, 9, 1, 4, 4 ) << QgsPoint( Qgis::WkbType::PointZM, 1, 1, 1, 7 ) );
+  poly1.addInteriorRing( ring1 );
 
   QgsCurvePolygon poly3( poly1 );
   QCOMPARE( poly1, poly3 );
 
   QgsCurvePolygon poly4;
+  QgsCircularString *ext2 = new QgsCircularString();
+  ext2->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZ, 0, 0, 1 )
+                   << QgsPoint( Qgis::WkbType::PointZ, 0, 10, 2 ) << QgsPoint( Qgis::WkbType::PointZ, 10, 10, 3 )
+                   << QgsPoint( Qgis::WkbType::PointZ, 10, 0, 4 ) << QgsPoint( Qgis::WkbType::PointZ, 0, 0, 1 ) );
+  poly4.setExteriorRing( ext2 );
+  QgsCircularString *ring2 = new QgsCircularString();
+  ring2->setPoints( QgsPointSequence() << QgsPoint( Qgis::WkbType::PointZ, 1, 1, 1 )
+                    << QgsPoint( Qgis::WkbType::PointZ, 1, 9, 2 ) << QgsPoint( Qgis::WkbType::PointZ, 9, 9, 3 )
+                    << QgsPoint( Qgis::WkbType::PointZ, 9, 1, 4 ) << QgsPoint( Qgis::WkbType::PointZ, 1, 1, 1 ) );
+  poly4.addInteriorRing( ring2 );
+  QVERIFY( poly4.exteriorRing() );
+  QCOMPARE( poly4.numInteriorRings(), 1 );
+  QVERIFY( poly4.interiorRing( 0 ) );
+  QVERIFY( poly2 != poly4 );
+
   poly4 = poly2;
   QCOMPARE( poly2, poly4 );
   poly4 = poly1;