diff --git a/gameboy/graphics.lua b/gameboy/graphics.lua
index 070cc8c..5726e6e 100644
--- a/gameboy/graphics.lua
+++ b/gameboy/graphics.lua
@@ -556,6 +556,10 @@ local function draw_sprites_into_scanline(scanline, bg_index)
 end
 
 graphics.draw_scanline = function(scanline)
+  if scanline < 0 or scanline > 143 then
+    print("Bad scanline: ", scanline)
+    return
+  end
   local bg_y = scanline + io.ram[ports.SCY]
   local bg_x = io.ram[ports.SCX]
   -- wrap the map in the Y direction
diff --git a/gameboy/init.lua b/gameboy/init.lua
index 5fc4995..760ba80 100644
--- a/gameboy/init.lua
+++ b/gameboy/init.lua
@@ -85,9 +85,9 @@ gameboy.run_until_vblank = function()
 end
 
 gameboy.run_until_hblank = function()
-  local old_scanline = gameboy.graphics.scanline()
+  local old_scanline = gameboy.io.ram[gameboy.io.ports.LY]
   local instructions = 0
-  while old_scanline == gameboy.graphics.scanline() and instructions < 100000  do
+  while old_scanline == gameboy.io.ram[gameboy.io.ports.LY] and instructions < 100000  do
     gameboy.step()
     instructions = instructions + 1
   end
diff --git a/gameboy/rom_header.lua b/gameboy/rom_header.lua
index 16987f5..c6f7570 100644
--- a/gameboy/rom_header.lua
+++ b/gameboy/rom_header.lua
@@ -40,9 +40,10 @@ rom_header.parse_cartridge_header = function(data)
   header.title = extract_string(data, 0x134, 0x143)
   header.manufacturer = extract_string(data, 0x13F, 0x142)
 
-  local cgb = bit32.band(data[0x143], 0x8) ~= 0
+  local cgb = (bit32.band(data[0x143], 0x80) ~= 0)
   if cgb then
     header.color = true
+    header.title = extract_string(data, 0x134, 0x13E)
   else
     header.color = false
   end