diff --git a/winsup/w32api/ChangeLog b/winsup/w32api/ChangeLog
index 95e5aeaee..471798955 100644
--- a/winsup/w32api/ChangeLog
+++ b/winsup/w32api/ChangeLog
@@ -1,3 +1,8 @@
+2011-03-05  Chris Sutcliffe  <ir0nh34d@users.sourceforge.net>
+
+	* include/winbase.h (PSAPI_WORKING_SET_BLOCK,
+	PSAPI_WORKING_SET_INFORMATION): Define.
+
 2011-03-05  Chris Sutcliffe  <ir0nh34d@users.sourceforge.net>
 
 	* include/winbase.h (__GNUC_EXTENSION): Define, replacing __MINGW_EXTENSION.
diff --git a/winsup/w32api/include/winbase.h b/winsup/w32api/include/winbase.h
index acb90fa7c..c09f2065b 100644
--- a/winsup/w32api/include/winbase.h
+++ b/winsup/w32api/include/winbase.h
@@ -2647,6 +2647,22 @@ typedef PCACTCTXA PCACTCTX;
 #endif
 #endif
 
+typedef union _PSAPI_WORKING_SET_BLOCK {
+  ULONG_PTR Flags;
+  struct {
+    ULONG_PTR Protection  :5;
+    ULONG_PTR ShareCount  :3;
+    ULONG_PTR Shared  :1;
+    ULONG_PTR Reserved  :3;
+    ULONG_PTR VirtualPage  :20;
+  } ;
+} PSAPI_WORKING_SET_BLOCK, *PPSAPI_WORKING_SET_BLOCK;
+
+typedef struct _PSAPI_WORKING_SET_INFORMATION {
+  ULONG_PTR               NumberOfEntries;
+  PSAPI_WORKING_SET_BLOCK WorkingSetInfo[1];
+} PSAPI_WORKING_SET_INFORMATION, *PPSAPI_WORKING_SET_INFORMATION;
+
 #ifdef __cplusplus
 }
 #endif