diff --git a/configs/common/FSConfig.py b/configs/common/FSConfig.py
index eea6b2ad0..0b47fbb4c 100644
--- a/configs/common/FSConfig.py
+++ b/configs/common/FSConfig.py
@@ -553,9 +553,9 @@ def makeX86System(mem_mode, numCPUs=1, mdesc=None, self=None, Ruby=False):
     # In gem5 Pc::calcPciConfigAddr(), it required "assert(bus==0)",
     # but linux kernel cannot config PCI device if it was not connected to PCI bus,
     # so we fix PCI bus id to 0, and ISA bus id to 1.
-    pci_bus = X86IntelMPBus(bus_id = 0, bus_type='PCI')
+    pci_bus = X86IntelMPBus(bus_id = 0, bus_type='PCI   ')
     base_entries.append(pci_bus)
-    isa_bus = X86IntelMPBus(bus_id = 1, bus_type='ISA')
+    isa_bus = X86IntelMPBus(bus_id = 1, bus_type='ISA   ')
     base_entries.append(isa_bus)
     connect_busses = X86IntelMPBusHierarchy(bus_id=1,
             subtractive_decode=True, parent_bus=0)
diff --git a/src/arch/x86/bios/IntelMP.py b/src/arch/x86/bios/IntelMP.py
index 21f93eaad..a39061f23 100644
--- a/src/arch/x86/bios/IntelMP.py
+++ b/src/arch/x86/bios/IntelMP.py
@@ -115,7 +115,7 @@ class X86IntelMPBus(X86IntelMPBaseConfigEntry):
 
     bus_id = Param.UInt8(0, 'bus id assigned by the bios')
     bus_type = Param.String("", 'string that identify the bus type')
-    # Legal values for bus_type are:
+    # Legal values for bus_type are [space padded to 6 bytes]:
     #
     # "CBUS", "CBUSII", "EISA", "FUTURE", "INTERN", "ISA", "MBI", "MBII",
     # "MCA", "MPI", "MPSA", "NUBUS", "PCI", "PCMCIA", "TC", "VL", "VME",