diff --git a/examples/jsm/nodes/materials/NodeMaterial.js b/examples/jsm/nodes/materials/NodeMaterial.js
index d06eae93f3c321..cbdbc630b68b35 100644
--- a/examples/jsm/nodes/materials/NodeMaterial.js
+++ b/examples/jsm/nodes/materials/NodeMaterial.js
@@ -199,7 +199,7 @@ class NodeMaterial extends ShaderMaterial {
 		if ( this.flatShading === true ) {
 
 			const fdx = dFdx( positionView );
-			const fdy = dFdy( positionView.negate() ); // use -positionView ?
+			const fdy = dFdy( positionView );
 			const normalNode = fdx.cross( fdy ).normalize();
 
 			stack.assign( transformedNormalView, normalNode );
diff --git a/examples/jsm/renderers/webgpu/nodes/WGSLNodeBuilder.js b/examples/jsm/renderers/webgpu/nodes/WGSLNodeBuilder.js
index 75825698891a8c..8aaafba0ba50fe 100644
--- a/examples/jsm/renderers/webgpu/nodes/WGSLNodeBuilder.js
+++ b/examples/jsm/renderers/webgpu/nodes/WGSLNodeBuilder.js
@@ -58,7 +58,7 @@ const wgslTypeLib = {
 
 const wgslMethods = {
 	dFdx: 'dpdx',
-	dFdy: 'dpdy',
+	dFdy: '- dpdy',
 	mod: 'threejs_mod',
 	lessThanEqual: 'threejs_lessThanEqual',
 	inversesqrt: 'inverseSqrt'