diff --git a/src/mame/drivers/midyunit.cpp b/src/mame/drivers/midyunit.cpp
index ee540d3a4e6..b5bbeb9c96e 100644
--- a/src/mame/drivers/midyunit.cpp
+++ b/src/mame/drivers/midyunit.cpp
@@ -205,7 +205,7 @@ void midyunit_state::main_map(address_map &map)
 	map(0x01c00060, 0x01c0007f).rw(FUNC(midyunit_state::midyunit_protection_r), FUNC(midyunit_state::midyunit_cmos_enable_w));
 	map(0x01e00000, 0x01e0001f).w(FUNC(midyunit_state::midyunit_sound_w));
 	map(0x01f00000, 0x01f0001f).w(FUNC(midyunit_state::midyunit_control_w));
-	map(0x02000000, 0x05ffffff).r(FUNC(midyunit_state::midyunit_gfxrom_r)).share("gfx_rom");
+	map(0x02000000, 0x05ffffff).r(FUNC(midyunit_state::midyunit_gfxrom_r));
 	map(0xff800000, 0xffffffff).rom().region("user1", 0);
 }
 
diff --git a/src/mame/includes/midyunit.h b/src/mame/includes/midyunit.h
index 274be779e9b..ae474389950 100644
--- a/src/mame/includes/midyunit.h
+++ b/src/mame/includes/midyunit.h
@@ -37,7 +37,7 @@ public:
 		, m_term2_adc(*this, "adc")
 		, m_nvram(*this, "nvram")
 		, m_generic_paletteram_16(*this, "paletteram")
-		, m_gfx_rom(*this, "gfx_rom")
+		, m_gfx_rom(*this, "gfx_rom", 0x800000, ENDIANNESS_BIG)
 		, m_mainram(*this, "mainram")
 		, m_ports(*this, { { "IN0", "IN1", "IN2", "DSW", "UNK0", "UNK1" } })
 	{
@@ -111,7 +111,7 @@ private:
 	required_device<nvram_device> m_nvram;
 
 	required_shared_ptr<uint16_t> m_generic_paletteram_16;
-	optional_shared_ptr<uint8_t> m_gfx_rom;
+	memory_share_creator<uint8_t> m_gfx_rom;
 	required_shared_ptr<uint16_t> m_mainram;
 	optional_ioport_array<6> m_ports;