diff --git a/dlls/ntdll/loader.c b/dlls/ntdll/loader.c
index 1bfd8f1fba6..31d83236c47 100644
--- a/dlls/ntdll/loader.c
+++ b/dlls/ntdll/loader.c
@@ -3152,7 +3152,7 @@ void WINAPI LdrInitializeThunk( void *kernel_start, ULONG_PTR unknown2,
     if ((status = fixup_imports( wm, load_path )) != STATUS_SUCCESS) goto error;
     heap_set_debug_flags( GetProcessHeap() );
 
-    status = wine_call_on_stack( attach_process_dlls, wm, NtCurrentTeb()->Tib.StackBase );
+    status = wine_call_on_stack( attach_process_dlls, wm, (char *)NtCurrentTeb()->Tib.StackBase - page_size );
     if (status != STATUS_SUCCESS) goto error;
 
     virtual_release_address_space();
diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index e4896eae37f..a452c58a44d 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -1745,8 +1745,8 @@ void virtual_clear_thread_stack(void)
     void *stack = NtCurrentTeb()->Tib.StackLimit;
     size_t size = (char *)NtCurrentTeb()->Tib.StackBase - (char *)NtCurrentTeb()->Tib.StackLimit;
 
-    wine_anon_mmap( stack, size, PROT_READ | PROT_WRITE, MAP_FIXED );
-    if (force_exec_prot) mprotect( stack, size, PROT_READ | PROT_WRITE | PROT_EXEC );
+    wine_anon_mmap( stack, size - page_size, PROT_READ | PROT_WRITE, MAP_FIXED );
+    if (force_exec_prot) mprotect( stack, size - page_size, PROT_READ | PROT_WRITE | PROT_EXEC );
 }