diff --git a/zion/memory/user_stack_manager.cpp b/zion/memory/user_stack_manager.cpp
index ffb91ae..6226ab4 100644
--- a/zion/memory/user_stack_manager.cpp
+++ b/zion/memory/user_stack_manager.cpp
@@ -8,30 +8,17 @@ uint64_t UserStackManager::NewUserStack() {
     return freed_stacks_.PopFront();
   }
 
-  uint64_t stack = next_stack_;
   next_stack_ -= kUserStackSize;
+  uint64_t stack = next_stack_;
   if (stack <= kUserStackMin) {
     panic("Out of user stacks!");
   }
-  if (stack == kUserStackMax) {
-    // Add a additional page boudary between kernel and user space.
-    stack -= 0x1000;
-  }
-  EnsureResident(stack - 1, 1);
   return stack;
 }
 
-void UserStackManager::FreeUserStack(uint64_t stack_ptr) {
-  freed_stacks_.PushBack(stack_ptr);
-}
-
-bool UserStackManager::IsValidStack(uint64_t vaddr) {
-  if (vaddr < next_stack_ || vaddr > (kUserStackMax - 0x1000)) {
-    return false;
+void UserStackManager::FreeUserStack(uint64_t stack_base) {
+  if (stack_base & (kUserStackSize - 1)) {
+    dbgln("WARN freeing unaligned user stack {x}", stack_base);
   }
-  // Checks if the address is in the first page of the stack.
-  if (vaddr & 0xFF000) {
-    return true;
-  }
-  return false;
+  freed_stacks_.PushBack(stack_base);
 }
diff --git a/zion/memory/user_stack_manager.h b/zion/memory/user_stack_manager.h
index fa549c4..adfe94d 100644
--- a/zion/memory/user_stack_manager.h
+++ b/zion/memory/user_stack_manager.h
@@ -21,10 +21,7 @@ class UserStackManager {
   UserStackManager(const UserStackManager&) = delete;
 
   uint64_t NewUserStack();
-  void FreeUserStack(uint64_t stack_ptr);
-
-  // Used to check if we should page in this address.
-  bool IsValidStack(uint64_t vaddr);
+  void FreeUserStack(uint64_t stack_base);
 
  private:
   uint64_t next_stack_ = kUserStackMax;
diff --git a/zion/object/address_space.cpp b/zion/object/address_space.cpp
index 398bfc2..196593d 100644
--- a/zion/object/address_space.cpp
+++ b/zion/object/address_space.cpp
@@ -18,12 +18,18 @@ AddressSpace::AddressSpace() {
   InitializePml4(cr3_);
 }
 
-uint64_t AddressSpace::AllocateUserStack() {
-  return user_stacks_.NewUserStack();
+glcr::ErrorOr<uint64_t> AddressSpace::AllocateUserStack() {
+  uint64_t base = user_stacks_.NewUserStack();
+  auto mem_object = glcr::StaticCastRefPtr<MemoryObject>(
+      glcr::MakeRefCounted<VariableMemoryObject>(kUserStackSize));
+  RET_ERR(MapInMemoryObject(base, mem_object));
+  return base;
 }
 
-void AddressSpace::FreeUserStack(uint64_t rsp) {
-  return user_stacks_.FreeUserStack(rsp);
+glcr::ErrorCode AddressSpace::FreeUserStack(uint64_t base) {
+  RET_ERR(FreeAddressRange(base, base + kUserStackSize));
+  user_stacks_.FreeUserStack(base);
+  return glcr::OK;
 }
 
 uint64_t AddressSpace::GetNextMemMapAddr(uint64_t size, uint64_t align) {
@@ -70,11 +76,6 @@ bool AddressSpace::HandlePageFault(uint64_t vaddr) {
     return false;
   }
 
-  if (user_stacks_.IsValidStack(vaddr)) {
-    MapPage(cr3_, vaddr, phys_mem::AllocatePage());
-    return true;
-  }
-
   auto offset_or = mapping_tree_.GetPhysicalPageAtVaddr(vaddr);
   if (!offset_or.ok()) {
     return false;
diff --git a/zion/object/address_space.h b/zion/object/address_space.h
index d6aebd7..0be9db1 100644
--- a/zion/object/address_space.h
+++ b/zion/object/address_space.h
@@ -65,8 +65,8 @@ class AddressSpace : public KernelObject {
   uint64_t cr3() { return cr3_; }
 
   // User Mappings.
-  uint64_t AllocateUserStack();
-  void FreeUserStack(uint64_t);
+  glcr::ErrorOr<uint64_t> AllocateUserStack();
+  [[nodiscard]] glcr::ErrorCode FreeUserStack(uint64_t stack_base);
   uint64_t GetNextMemMapAddr(uint64_t size, uint64_t align);
 
   // Maps in a memory object at a specific address.
diff --git a/zion/object/thread.cpp b/zion/object/thread.cpp
index 76d5acd..701792c 100644
--- a/zion/object/thread.cpp
+++ b/zion/object/thread.cpp
@@ -72,14 +72,15 @@ void Thread::Init() {
 #if K_THREAD_DEBUG
   dbgln("Thread start.", pid(), id_);
 #endif
-  uint64_t rsp_ = process_.vmas()->AllocateUserStack();
-  // TODO: Investigate this further but without this GCC
-  // will emit movaps calls to non-16-bit-aligned stack
-  // addresses.
-  rsp_ -= 0x8;
-  *reinterpret_cast<uint64_t*>(rsp_) = kStackBaseSentinel;
+  auto stack_or = process_.vmas()->AllocateUserStack();
+  if (!stack_or.ok()) {
+    panic("Unable to allocate user stack: {}", stack_or.error());
+  }
+  user_stack_base_ = stack_or.value();
+  uint64_t rsp = user_stack_base_ + kUserStackSize - 0x8;
+  *reinterpret_cast<uint64_t*>(rsp) = kStackBaseSentinel;
   SetRsp0(rsp0_start_);
-  jump_user_space(rip_, rsp_, arg1_, arg2_);
+  jump_user_space(rip_, rsp, arg1_, arg2_);
 }
 void Thread::SetState(State state) {
   if (IsDying()) {
@@ -113,7 +114,8 @@ void Thread::Cleanup() {
   }
 
   // 1. Release User Stack
-  process_.vmas()->FreeUserStack(rsp_);
+  PANIC_ON_ERR(process_.vmas()->FreeUserStack(user_stack_base_),
+               "Unable to free user stack.");
 
   // 2. Unblock waiting threads.
   while (blocked_threads_.size() != 0) {
diff --git a/zion/object/thread.h b/zion/object/thread.h
index fcde8a8..53bee2b 100644
--- a/zion/object/thread.h
+++ b/zion/object/thread.h
@@ -78,9 +78,9 @@ class Thread : public KernelObject, public glcr::IntrusiveListNode<Thread> {
   uint64_t id_;
   State state_ = CREATED;
   bool is_kernel_ = false;
+  uint64_t user_stack_base_;
 
   // Startup Context for the thread.
-  uint64_t rsp_;
   uint64_t rip_;
   uint64_t arg1_;
   uint64_t arg2_;