diff --git a/src/device/disk.c b/src/device/disk.c
index 686261dc7c908a76ad20277bfb17b55cbd07664f..1ec49fb1924b1fb831eac520140bab2806bab74f 100644
--- a/src/device/disk.c
+++ b/src/device/disk.c
@@ -35,9 +35,14 @@ void init_disk() {
   add_pio_map ("disk", AUDIO_PORT, (void *)disk_base, space_size, disk_io_handler);
   add_mmio_map("disk", AUDIO_MMIO, (void *)disk_base, space_size, disk_io_handler);
 
-  fp = fopen("/home/yzh/projectn/nanos-lite/build/ramdisk.img", "r");
-  assert(fp);
-  fseek(fp, 0, SEEK_END);
-  disk_base[SIZE] = ftell(fp) / 512 + 1;
-  fseek(fp, 0, SEEK_SET);
+  const char *path ="/home/yzh/projectn/nanos-lite/build/ramdisk.img";
+  fp = fopen(path, "r");
+  if (fp) {
+    fseek(fp, 0, SEEK_END);
+    disk_base[SIZE] = ftell(fp) / 512 + 1;
+    fseek(fp, 0, SEEK_SET);
+  } else {
+    Log("Can not open %s. Disable disk...", path);
+    disk_base[SIZE] = 0;
+  }
 }
diff --git a/src/device/vga.c b/src/device/vga.c
index 1855653f44018d77f518ea8f328718872d356419..474de347c4041592abb513fc5d092b05a8d81fab 100644
--- a/src/device/vga.c
+++ b/src/device/vga.c
@@ -26,8 +26,10 @@
 #define VGACTL_PORT 0x100 // Note that this is not the standard
 #define VGACTL_MMIO 0xa1000100
 
+#ifdef SHOW_SCREEN
 static SDL_Renderer *renderer = NULL;
 static SDL_Texture *texture = NULL;
+#endif
 
 static uint32_t (*vmem) [SCREEN_W] = NULL;
 static uint32_t *vgactl_port_base = NULL;