diff --git a/src/mame/drivers/einstein.cpp b/src/mame/drivers/einstein.cpp
index 47b1b719576..2d689fd1f63 100644
--- a/src/mame/drivers/einstein.cpp
+++ b/src/mame/drivers/einstein.cpp
@@ -419,8 +419,11 @@ WRITE8_MEMBER(einstein_state::evdpint_msk_w)
 
 READ8_MEMBER( einstein_state::rom_r )
 {
-	m_rom_enabled ^= 1;
-	m_bank1->set_entry(m_rom_enabled);
+	if (!machine().side_effects_disabled())
+	{
+		m_rom_enabled ^= 1;
+		m_bank1->set_entry(m_rom_enabled);
+	}
 
 	return 0xff;
 }