Index: kernel/arch/amd64/src/userspace.c
===================================================================
--- kernel/arch/amd64/src/userspace.c	(revision 88dfee72b892efbc89d6fc68db4a2e3de85ea013)
+++ kernel/arch/amd64/src/userspace.c	(revision 0bbd13e274302c7c89dd4ea7cad7dbcc3ecfc524)
@@ -55,5 +55,5 @@
 	asm volatile (
 		"pushq %[udata_des]\n"
-		"pushq %[stack_size]\n"
+		"pushq %[stack_top]\n"
 		"pushq %[ipl]\n"
 		"pushq %[utext_des]\n"
@@ -65,5 +65,6 @@
 		"iretq\n"
 		:: [udata_des] "i" (GDT_SELECTOR(UDATA_DES) | PL_USER),
-		   [stack_size] "r" (kernel_uarg->uspace_stack + STACK_SIZE),
+		   [stack_top] "r" ((uint8_t *) kernel_uarg->uspace_stack +
+		       kernel_uarg->uspace_stack_size),
 		   [ipl] "r" (ipl),
 		   [utext_des] "i" (GDT_SELECTOR(UTEXT_DES) | PL_USER),
@@ -74,6 +75,5 @@
 	
 	/* Unreachable */
-	while (1)
-		;
+	while (1);
 }