diff --git a/arch/src/aarch64/layout.rs b/arch/src/aarch64/layout.rs
index 8ef2bcda3..22a74edce 100644
--- a/arch/src/aarch64/layout.rs
+++ b/arch/src/aarch64/layout.rs
@@ -43,7 +43,7 @@
 //
 //
 
-use vm_memory::{GuestAddress, GuestUsize};
+use vm_memory::GuestAddress;
 
 /// Below this address will reside the GIC, above this address will reside the MMIO devices.
 pub const MAPPED_IO_START: u64 = 0x0900_0000;
@@ -61,7 +61,7 @@ pub const MEM_32BIT_DEVICES_SIZE: u64 = 0x3000_0000;
 
 /// PCI MMCONFIG space (start: after the device space at 1 GiB, length: 256MiB)
 pub const PCI_MMCONFIG_START: GuestAddress = GuestAddress(0x4000_0000);
-pub const PCI_MMCONFIG_SIZE: GuestUsize = 256 << 20;
+pub const PCI_MMCONFIG_SIZE: u64 = 256 << 20;
 
 /// Start of RAM on 64 bit ARM.
 pub const RAM_64BIT_START: u64 = 0x8000_0000;
diff --git a/arch/src/x86_64/layout.rs b/arch/src/x86_64/layout.rs
index d519b49e6..cb8c0c29e 100644
--- a/arch/src/x86_64/layout.rs
+++ b/arch/src/x86_64/layout.rs
@@ -7,7 +7,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE-BSD-3-Clause file.
 
-use vm_memory::{GuestAddress, GuestUsize};
+use vm_memory::GuestAddress;
 
 /*
 
@@ -81,22 +81,22 @@ pub const HIGH_RAM_START: GuestAddress = GuestAddress(0x100000);
 
 // ** 32-bit reserved area (start: 3GiB, length: 1GiB) **
 pub const MEM_32BIT_RESERVED_START: GuestAddress = GuestAddress(0xc000_0000);
-pub const MEM_32BIT_RESERVED_SIZE: GuestUsize = 1024 << 20;
+pub const MEM_32BIT_RESERVED_SIZE: u64 = 1024 << 20;
 
 // == Fixed constants within the "32-bit reserved" range ==
 
 // Sub range: 32-bit PCI devices (start: 3GiB, length: 640Mib)
 pub const MEM_32BIT_DEVICES_START: GuestAddress = MEM_32BIT_RESERVED_START;
-pub const MEM_32BIT_DEVICES_SIZE: GuestUsize = 640 << 20;
+pub const MEM_32BIT_DEVICES_SIZE: u64 = 640 << 20;
 
 // PCI MMCONFIG space (start: after the device space, length: 256MiB)
 pub const PCI_MMCONFIG_START: GuestAddress =
     GuestAddress(MEM_32BIT_DEVICES_START.0 + MEM_32BIT_DEVICES_SIZE);
-pub const PCI_MMCONFIG_SIZE: GuestUsize = 256 << 20;
+pub const PCI_MMCONFIG_SIZE: u64 = 256 << 20;
 
 // IOAPIC
 pub const IOAPIC_START: GuestAddress = GuestAddress(0xfec0_0000);
-pub const IOAPIC_SIZE: GuestUsize = 0x20;
+pub const IOAPIC_SIZE: u64 = 0x20;
 
 // APIC
 pub const APIC_START: GuestAddress = GuestAddress(0xfee0_0000);