diff --git a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.MemoryDomains.cs b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.MemoryDomains.cs
index f368fadde1..d363396d4a 100644
--- a/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.MemoryDomains.cs
+++ b/src/BizHawk.Emulation.Cores/Arcades/MAME/MAME.MemoryDomains.cs
@@ -106,6 +106,7 @@ namespace BizHawk.Emulation.Cores.Arcades.MAME
 				null, dataWidth));
 
 			_memoryDomains = new MemoryDomainList(domains);
+			((MemoryDomainList)_memoryDomains).SystemBus = _memoryDomains[deviceName + " : System Bus"];
 			(ServiceProvider as BasicServiceProvider).Register<IMemoryDomains>(_memoryDomains);
 		}
 	}