diff --git a/scene/resources/material.cpp b/scene/resources/material.cpp
index abb3381c4ee4..2a72913515d2 100644
--- a/scene/resources/material.cpp
+++ b/scene/resources/material.cpp
@@ -773,6 +773,9 @@ void BaseMaterial3D::_update_shader() {
 
 	if (!flags[FLAG_UV1_USE_TRIPLANAR]) {
 		code += "	UV=UV*uv1_scale.xy+uv1_offset.xy;\n";
+		code += "	if (determinant(mat3(WORLD_MATRIX)) < 0.0) {";
+		code += "		NORMAL = -NORMAL;";
+		code += "	}";
 	}
 
 	switch (billboard_mode) {