diff --git a/tiny_obj_loader.cc b/tiny_obj_loader.cc
index 51de34b..999a9a0 100644
--- a/tiny_obj_loader.cc
+++ b/tiny_obj_loader.cc
@@ -217,6 +217,7 @@ void InitMaterial(material_t& material) {
   material.illum = 0;
   material.dissolve = 1.f;
   material.shininess = 1.f;
+  material.ior = 1.f;
   material.unknown_parameter.clear();
 }