diff --git a/src/arch/emulate.rs b/src/arch/emulate.rs
index 2e290b6810..c4210d631e 100644
--- a/src/arch/emulate.rs
+++ b/src/arch/emulate.rs
@@ -19,6 +19,7 @@ impl Arch for EmulateArch {
     const PAGE_ENTRY_SHIFT: usize = X8664Arch::PAGE_ENTRY_SHIFT;
     const PAGE_LEVELS: usize = X8664Arch::PAGE_LEVELS;
 
+    const ENTRY_ADDRESS_SHIFT: usize = X8664Arch::ENTRY_ADDRESS_SHIFT;
     const ENTRY_FLAG_PRESENT: usize = X8664Arch::ENTRY_FLAG_PRESENT;
     const ENTRY_FLAG_WRITABLE: usize = X8664Arch::ENTRY_FLAG_WRITABLE;
     const ENTRY_FLAG_USER: usize = X8664Arch::ENTRY_FLAG_USER;
diff --git a/src/arch/mod.rs b/src/arch/mod.rs
index 3b9075fb39..1dbd31a096 100644
--- a/src/arch/mod.rs
+++ b/src/arch/mod.rs
@@ -10,6 +10,7 @@ pub trait Arch {
     const PAGE_ENTRY_SHIFT: usize;
     const PAGE_LEVELS: usize;
 
+    const ENTRY_ADDRESS_SHIFT: usize;
     const ENTRY_FLAG_PRESENT: usize;
     const ENTRY_FLAG_WRITABLE: usize;
     const ENTRY_FLAG_USER: usize;
@@ -21,13 +22,13 @@ pub trait Arch {
     const PAGE_OFFSET_MASK: usize = Self::PAGE_SIZE - 1;
     const PAGE_ADDRESS_SHIFT: usize = Self::PAGE_LEVELS * Self::PAGE_ENTRY_SHIFT + Self::PAGE_SHIFT;
     const PAGE_ADDRESS_SIZE: usize = 1 << Self::PAGE_ADDRESS_SHIFT;
-    const PAGE_ADDRESS_MASK: usize = Self::PAGE_ADDRESS_SIZE - 1 - Self::PAGE_OFFSET_MASK;
+    const PAGE_ADDRESS_MASK: usize = Self::PAGE_ADDRESS_SIZE - Self::PAGE_SIZE;
     const PAGE_ENTRY_SIZE: usize = 1 << (Self::PAGE_SHIFT - Self::PAGE_ENTRY_SHIFT);
     const PAGE_ENTRIES: usize = 1 << Self::PAGE_ENTRY_SHIFT;
     const PAGE_ENTRY_MASK: usize = Self::PAGE_ENTRIES - 1;
 
-    //TODO: allow this to differ from page address mask
-    const ENTRY_ADDRESS_MASK: usize = Self::PAGE_ADDRESS_MASK;
+    const ENTRY_ADDRESS_SIZE: usize = 1 << Self::ENTRY_ADDRESS_SHIFT;
+    const ENTRY_ADDRESS_MASK: usize = Self::ENTRY_ADDRESS_SIZE - Self::PAGE_SIZE;
     const ENTRY_FLAGS_MASK: usize = !Self::ENTRY_ADDRESS_MASK;
 
     unsafe fn init() -> &'static [MemoryArea];
diff --git a/src/arch/x86_64.rs b/src/arch/x86_64.rs
index 41d674d949..6197e7cf54 100644
--- a/src/arch/x86_64.rs
+++ b/src/arch/x86_64.rs
@@ -10,6 +10,7 @@ impl Arch for X8664Arch {
     const PAGE_ENTRY_SHIFT: usize = 9; // 512 entries, 8 bytes each
     const PAGE_LEVELS: usize = 4; // PML4, PDP, PD, PT
 
+    const ENTRY_ADDRESS_SHIFT: usize = 52;
     const ENTRY_FLAG_PRESENT: usize = 1 << 0;
     const ENTRY_FLAG_WRITABLE: usize = 1 << 1;
     const ENTRY_FLAG_USER: usize = 1 << 2;
@@ -62,7 +63,8 @@ mod tests {
         assert_eq!(X8664Arch::PAGE_ENTRIES, 512);
         assert_eq!(X8664Arch::PAGE_ENTRY_MASK, 0x1FF);
 
-        assert_eq!(X8664Arch::ENTRY_ADDRESS_MASK, 0x0000_FFFF_FFFF_F000);
-        assert_eq!(X8664Arch::ENTRY_FLAGS_MASK, 0xFFFF_0000_0000_0FFF);
+        assert_eq!(X8664Arch::ENTRY_ADDRESS_SIZE, 0x0010_0000_0000_0000);
+        assert_eq!(X8664Arch::ENTRY_ADDRESS_MASK, 0x000F_FFFF_FFFF_F000);
+        assert_eq!(X8664Arch::ENTRY_FLAGS_MASK, 0xFFF0_0000_0000_0FFF);
     }
 }