diff --git a/libs/vkd3d-shader/d3d_asm.c b/libs/vkd3d-shader/d3d_asm.c
index 2c510809..ac63624c 100644
--- a/libs/vkd3d-shader/d3d_asm.c
+++ b/libs/vkd3d-shader/d3d_asm.c
@@ -1066,6 +1066,10 @@ static void shader_dump_register(struct vkd3d_d3d_asm_compiler *compiler, const
             shader_addline(buffer, "oStencilRef");
             break;
 
+        case VKD3DSPR_UNDEF:
+            shader_addline(buffer, "undef");
+            break;
+
         default:
             shader_addline(buffer, "<unhandled_rtype(%#x)>", reg->type);
             break;