diff --git a/src/core/geometry/qgsgeometry.cpp b/src/core/geometry/qgsgeometry.cpp
index 325f1564c87..462434076f4 100644
--- a/src/core/geometry/qgsgeometry.cpp
+++ b/src/core/geometry/qgsgeometry.cpp
@@ -1241,7 +1241,17 @@ Qgis::GeometryOperationResult QgsGeometry::reshapeGeometry( const QgsLineString
     return Qgis::GeometryOperationResult::InvalidBaseGeometry;
   }
 
-  QgsGeos geos( d->geometry.get() );
+  // We're trying adding the reshape line's vertices to the geometry so that
+  // snap to segment always produces a valid reshape
+  QgsPointSequence reshapePoints;
+  reshapeLineString.points( reshapePoints );
+  QgsGeometry tmpGeom( *this );
+  for ( const QgsPoint &v : std::as_const( reshapePoints ) )
+  {
+    tmpGeom.addTopologicalPoint( v );
+  }
+
+  QgsGeos geos( tmpGeom.get() );
   QgsGeometryEngine::EngineOperationResult errorCode = QgsGeometryEngine::Success;
   mLastError.clear();
   std::unique_ptr< QgsAbstractGeometry > geom( geos.reshapeGeometry( reshapeLineString, &errorCode, &mLastError ) );
diff --git a/tests/src/app/testqgsmaptoolreshape.cpp b/tests/src/app/testqgsmaptoolreshape.cpp
index cf7ee1e5162..f8c208a5919 100644
--- a/tests/src/app/testqgsmaptoolreshape.cpp
+++ b/tests/src/app/testqgsmaptoolreshape.cpp
@@ -50,6 +50,7 @@ class TestQgsMapToolReshape : public QObject
     void reshapeWithBindingLine();
     void testWithTracing();
     void testKeepDirection();
+    void testWithSnapToSegment();
 
   private:
     QgisApp *mQgisApp = nullptr;
@@ -531,11 +532,42 @@ void TestQgsMapToolReshape::testKeepDirection()
   QString wkt3 = QStringLiteral( "LineString (13 1, 12 1, 12 3, 13 3, 14 3, 14 5, 13 5, 12 5, 12 7, 13 7, 13 8, 19 11, 25 8, 25 0, 13 0, 13 1)" );
   QCOMPARE( mLayerLine->getFeature( 3 ).geometry().asWkt(), wkt3 );
 
+  // undo the three changes
+  mLayerLine->undoStack()->undo();
+  mLayerLine->undoStack()->undo();
+  mLayerLine->undoStack()->undo();
+
   // activate back snapping
   cfg.setEnabled( true );
   mCanvas->snappingUtils()->setConfig( cfg );
 }
 
+void TestQgsMapToolReshape::testWithSnapToSegment()
+{
+  TestQgsMapToolAdvancedDigitizingUtils utils( mCaptureTool );
+  mCanvas->setLayers( { mLayerPolygonZ } );
+  mCanvas->setCurrentLayer( mLayerPolygonZ );
+  mCanvas->setDestinationCrs( mLayerPolygonZ->crs() );
+
+  QgsSnappingConfig cfg = mCanvas->snappingUtils()->config();
+  cfg.setTypeFlag( static_cast<Qgis::SnappingTypes>( Qgis::SnappingType::Segment ) );
+  mCanvas->snappingUtils()->setConfig( cfg );
+
+  QCOMPARE( mLayerPolygonZ->getFeature( 1 ).geometry().asWkt(), QStringLiteral( "Polygon Z ((7 5 4, 3 2 1, 0 1 2, 7 5 4))" ) );
+
+  // snap to segment on a diagonal
+  utils.mouseClick( 5.5, 4.5, Qt::LeftButton, {}, true );
+  utils.mouseClick( 1, 5, Qt::LeftButton );
+  utils.mouseClick( 1, 2, Qt::LeftButton, {}, true );
+  utils.mouseClick( 1, 2, Qt::RightButton );
+
+  QCOMPARE( mLayerPolygonZ->getFeature( 1 ).geometry().asWkt( 1 ), QStringLiteral( "Polygon Z ((1.2 1.7 333, 1 5 333, 5.7 4.2 333, 7 5 4, 3 2 1, 0 1 2, 1.2 1.7 333))" ) );
+
+  mLayerLine->undoStack()->undo();
+
+  cfg.setTypeFlag( static_cast<Qgis::SnappingTypes>( Qgis::SnappingType::Vertex | Qgis::SnappingType::Segment ) );
+  mCanvas->snappingUtils()->setConfig( cfg );
+}
 
 QGSTEST_MAIN( TestQgsMapToolReshape )
 #include "testqgsmaptoolreshape.moc"