diff --git a/sortix/kernel.cpp b/sortix/kernel.cpp
index ecee8f6f..95914283 100644
--- a/sortix/kernel.cpp
+++ b/sortix/kernel.cpp
@@ -56,8 +56,8 @@ using namespace Maxsi;
 
 void* RunApplication(void* Parameter);
 
+// Keep the stack size aligned with $CPU/base.s
 extern "C" { size_t stack[64*1024] = {0}; }
-extern "C" { size_t stackend = 0; }
 
 namespace Sortix
 {
diff --git a/sortix/x64/base.s b/sortix/x64/base.s
index 18fe106e..ab401ac3 100644
--- a/sortix/x64/base.s
+++ b/sortix/x64/base.s
@@ -41,7 +41,8 @@ _beginkernel:
 	movw $0x758, 0xB83F8
 
 	# Initialize the stack pointer.
-	movq $stackend, %rsp
+	movq $stack, %rsp
+	addq $65536, %rsp # 64 KiB, see kernel.cpp
 
 	# Reset EFLAGS.
 	# pushl	$0
diff --git a/sortix/x86-family/memorymanagement.cpp b/sortix/x86-family/memorymanagement.cpp
index 07140deb..414c5d0b 100644
--- a/sortix/x86-family/memorymanagement.cpp
+++ b/sortix/x86-family/memorymanagement.cpp
@@ -291,6 +291,12 @@ namespace Sortix
 
 		addr_t SwitchAddressSpace(addr_t addrspace)
 		{
+			if ( currentdir != Page::AlignDown(currentdir) )
+			{
+				PanicF("Attempted to switch to address space 0x%zx, but it "
+				       "wasn't page aligned!", currentdir);
+			}
+
 			// Don't switch if we are already there.
 			if ( addrspace == currentdir ) { return currentdir; }
 
diff --git a/sortix/x86/base.s b/sortix/x86/base.s
index 509cfa71..c02c11b3 100644
--- a/sortix/x86/base.s
+++ b/sortix/x86/base.s
@@ -31,8 +31,9 @@
 .type _beginkernel, @function
 beginkernel:
 _beginkernel:
-	# Initialize the stack pointer.
-	mov	$stackend, %esp
+	# Initialize the stack pointer. The magic value is from kernel.cpp.
+	movl $stack, %esp
+	addl $65536, %esp # 64 KiB, see kernel.cpp
 
 	# Reset EFLAGS.
 	# pushl	$0