diff --git a/src/xenia/cpu/thread_state.cc b/src/xenia/cpu/thread_state.cc
index 54d795f24..73af5b2d6 100644
--- a/src/xenia/cpu/thread_state.cc
+++ b/src/xenia/cpu/thread_state.cc
@@ -46,9 +46,11 @@ ThreadState::ThreadState(Processor* processor, uint32_t thread_id,
   backend_data_ = processor->backend()->AllocThreadData();
 
   if (!stack_address) {
+    // We must always allocate 64K as a guard region before stacks, as we can
+    // only Protect() on system page granularity.
     stack_size = (stack_size + 0xFFF) & 0xFFFFF000;
     uint32_t stack_alignment = (stack_size & 0xF000) ? 0x1000 : 0x10000;
-    uint32_t stack_padding = stack_alignment * 1;
+    uint32_t stack_padding = xe::page_size();  // Host page size.
     uint32_t actual_stack_size = stack_padding + stack_size;
     bool top_down;
     switch (stack_type) {
diff --git a/src/xenia/memory.cc b/src/xenia/memory.cc
index e78edfd98..9c45bb11a 100644
--- a/src/xenia/memory.cc
+++ b/src/xenia/memory.cc
@@ -852,12 +852,19 @@ bool BaseHeap::Protect(uint32_t address, uint32_t size, uint32_t protect) {
   }
 
   // Attempt host change (hopefully won't fail).
-  DWORD new_protect = ToWin32ProtectFlags(protect);
-  DWORD old_protect;
-  if (!VirtualProtect(membase_ + heap_base_ + start_page_number * page_size_,
-                      page_count * page_size_, new_protect, &old_protect)) {
-    XELOGE("BaseHeap::Protect failed due to host VirtualProtect failure");
-    return false;
+  // We can only do this if our size matches system page granularity.
+  if (page_size_ == xe::page_size() ||
+      ((page_count * page_size_) % xe::page_size() == 0) &&
+          ((start_page_number * page_size_) % xe::page_size() == 0)) {
+    DWORD new_protect = ToWin32ProtectFlags(protect);
+    DWORD old_protect;
+    if (!VirtualProtect(membase_ + heap_base_ + start_page_number * page_size_,
+                        page_count * page_size_, new_protect, &old_protect)) {
+      XELOGE("BaseHeap::Protect failed due to host VirtualProtect failure");
+      return false;
+    }
+  } else {
+    XELOGW("BaseHeap::Protect: ignoring request as not 64k page aligned");
   }
 
   // Perform table change.