diff --git a/ChangeLog b/ChangeLog
index ab3338da79..41dc2538a0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Oct 27 18:14:27 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* win32/win32.c (rb_w32_getppid): support Win64.
+
 Wed Oct 27 15:07:19 2010  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* thread_win32.c (w32_error): should get error no only once, because
diff --git a/win32/win32.c b/win32/win32.c
index 32b468f15c..d28050f3e6 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -4711,10 +4711,10 @@ rb_w32_getppid(void)
 	    struct {
 		long ExitStatus;
 		void* PebBaseAddress;
-		ULONG AffinityMask;
-		ULONG BasePriority;
-		ULONG UniqueProcessId;
-		ULONG ParentProcessId;
+		uintptr_t AffinityMask;
+		uintptr_t BasePriority;
+		uintptr_t UniqueProcessId;
+		uintptr_t ParentProcessId;
 	    } pbi;
 	    ULONG len;
 	    long ret = pNtQueryInformationProcess(GetCurrentProcess(), 0, &pbi, sizeof(pbi), &len);