diff --git a/src/xenia/cpu/mmio_handler.cc b/src/xenia/cpu/mmio_handler.cc
index 53b2e299f..0be69a72b 100644
--- a/src/xenia/cpu/mmio_handler.cc
+++ b/src/xenia/cpu/mmio_handler.cc
@@ -12,6 +12,7 @@
 #include "xenia/base/assert.h"
 #include "xenia/base/byte_order.h"
 #include "xenia/base/math.h"
+#include "xenia/base/memory.h"
 
 namespace BE {
 #include <beaengine/BeaEngine.h>
@@ -90,6 +91,12 @@ uintptr_t MMIOHandler::AddPhysicalWriteWatch(uint32_t guest_address,
   uint32_t base_address = guest_address;
   assert_true(base_address < 0x1FFFFFFF);
 
+  // Can only protect sizes matching system page size.
+  // This means we need to round up, which will cause spurious access
+  // violations and invalidations.
+  // TODO(benvanik): only invalidate if actually within the region?
+  length = xe::round_up(length, xe::page_size());
+
   // Add to table. The slot reservation may evict a previous watch, which
   // could include our target, so we do it first.
   auto entry = new WriteWatchEntry();
@@ -106,8 +113,6 @@ uintptr_t MMIOHandler::AddPhysicalWriteWatch(uint32_t guest_address,
   DWORD old_protect;
   VirtualProtect(physical_membase_ + entry->address, entry->length,
                  PAGE_READONLY, &old_protect);
-  VirtualProtect(virtual_membase_ + entry->address, entry->length,
-                 PAGE_READONLY, &old_protect);
   VirtualProtect(virtual_membase_ + 0xA0000000 + entry->address, entry->length,
                  PAGE_READONLY, &old_protect);
   VirtualProtect(virtual_membase_ + 0xC0000000 + entry->address, entry->length,
@@ -122,8 +127,6 @@ void MMIOHandler::ClearWriteWatch(WriteWatchEntry* entry) {
   DWORD old_protect;
   VirtualProtect(physical_membase_ + entry->address, entry->length,
                  PAGE_READWRITE, &old_protect);
-  VirtualProtect(virtual_membase_ + entry->address, entry->length,
-                 PAGE_READWRITE, &old_protect);
   VirtualProtect(virtual_membase_ + 0xA0000000 + entry->address, entry->length,
                  PAGE_READWRITE, &old_protect);
   VirtualProtect(virtual_membase_ + 0xC0000000 + entry->address, entry->length,
diff --git a/src/xenia/memory.cc b/src/xenia/memory.cc
index 9c45bb11a..ceb4cab2d 100644
--- a/src/xenia/memory.cc
+++ b/src/xenia/memory.cc
@@ -804,12 +804,17 @@ bool BaseHeap::Release(uint32_t base_address, uint32_t* out_region_size) {
     PLOGE("BaseHeap::Release failed due to host VirtualFree failure");
     return false;
   }*/
-  // Instead, we just protect it.
-  DWORD old_protect;
-  if (!VirtualProtect(membase_ + heap_base_ + base_page_number * page_size_,
-                      base_page_entry.region_page_count * page_size_,
-                      PAGE_NOACCESS, &old_protect)) {
-    XELOGW("BaseHeap::Release failed due to host VirtualProtect failure");
+  // Instead, we just protect it, if we can.
+  if (page_size_ == xe::page_size() ||
+      ((base_page_entry.region_page_count * page_size_) % xe::page_size() ==
+       0) &&
+          ((base_page_number * page_size_) % xe::page_size() == 0)) {
+    DWORD old_protect;
+    if (!VirtualProtect(membase_ + heap_base_ + base_page_number * page_size_,
+                        base_page_entry.region_page_count * page_size_,
+                        PAGE_NOACCESS, &old_protect)) {
+      XELOGW("BaseHeap::Release failed due to host VirtualProtect failure");
+    }
   }
 
   // Perform table change.