diff --git a/ntoskrnl/ke/amd64/stubs.c b/ntoskrnl/ke/amd64/stubs.c
index f63485eb788..9f8ed16e0de 100644
--- a/ntoskrnl/ke/amd64/stubs.c
+++ b/ntoskrnl/ke/amd64/stubs.c
@@ -278,13 +278,11 @@ KiSwapProcess(IN PKPROCESS NewProcess,
               IN PKPROCESS OldProcess)
 {
     PKIPCR Pcr = (PKIPCR)KeGetPcr();
-#ifdef CONFIG_SMP
-    LONG SetMember;
 
+#ifdef CONFIG_SMP
     /* Update active processor mask */
-    SetMember = (LONG)Pcr->SetMember;
-    InterlockedXor((PLONG)&NewProcess->ActiveProcessors, SetMember);
-    InterlockedXor((PLONG)&OldProcess->ActiveProcessors, SetMember);
+    InterlockedXor64((PLONG64)&NewProcess->ActiveProcessors, Pcr->Prcb.SetMember);
+    InterlockedXor64((PLONG64)&OldProcess->ActiveProcessors, Pcr->Prcb.SetMember);
 #endif
 
     /* Update CR3 */
diff --git a/sdk/include/ndk/ketypes.h b/sdk/include/ndk/ketypes.h
index 839a0d77d74..7a8c614a8de 100644
--- a/sdk/include/ndk/ketypes.h
+++ b/sdk/include/ndk/ketypes.h
@@ -1988,7 +1988,7 @@ typedef struct _KPROCESS
     UCHAR Iopl;
     UCHAR Unused;
 #endif
-    volatile ULONG ActiveProcessors;
+    volatile KAFFINITY ActiveProcessors;
     ULONG KernelTime;
     ULONG UserTime;
     LIST_ENTRY ReadyListHead;