diff --git a/dlls/krnl386.exe16/kernel16_private.h b/dlls/krnl386.exe16/kernel16_private.h
index fbc1a5f8258..1e3935aa48a 100644
--- a/dlls/krnl386.exe16/kernel16_private.h
+++ b/dlls/krnl386.exe16/kernel16_private.h
@@ -169,9 +169,6 @@ extern THHOOK *pThhook DECLSPEC_HIDDEN;
     (((offset)+(size) <= pModule->mapping_size) ? \
      (memcpy( buffer, (const char *)pModule->mapping + (offset), (size) ), TRUE) : FALSE)
 
-#define CURRENT_STACK16 ((STACK16FRAME*)MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved)))
-#define CURRENT_DS      (CURRENT_STACK16->ds)
-
 /* push bytes on the 16-bit stack of a thread; return a segptr to the first pushed byte */
 static inline SEGPTR stack16_push( int size )
 {
diff --git a/dlls/krnl386.exe16/thunk.c b/dlls/krnl386.exe16/thunk.c
index e913a08f88c..832cc71d9be 100644
--- a/dlls/krnl386.exe16/thunk.c
+++ b/dlls/krnl386.exe16/thunk.c
@@ -1276,7 +1276,7 @@ void WINAPI __regs_K32Thk1632Epilog( CONTEXT *context )
    if (   code[5] == 0xFF && code[6] == 0x55 && code[7] == 0xFC
        && code[13] == 0x66 && code[14] == 0xCB)
    {
-      STACK16FRAME *frame16 = MapSL((SEGPTR)NtCurrentTeb()->WOW32Reserved);
+      STACK16FRAME *frame16 = CURRENT_STACK16;
       char *stack16 = (char *)(frame16 + 1);
       DWORD argSize = frame16->ebp - (DWORD)stack16;
       char *stack32 = (char *)frame16->frame32 - argSize;
diff --git a/dlls/toolhelp.dll16/toolhelp.c b/dlls/toolhelp.dll16/toolhelp.c
index 578d1ae7fab..5d7bf8f016e 100644
--- a/dlls/toolhelp.dll16/toolhelp.c
+++ b/dlls/toolhelp.dll16/toolhelp.c
@@ -718,15 +718,15 @@ BOOL16 WINAPI TimerCount16( TIMERINFO *pTimerInfo )
  */
 BOOL16 WINAPI SystemHeapInfo16( SYSHEAPINFO *pHeapInfo )
 {
-    STACK16FRAME* stack16 = MapSL((SEGPTR)NtCurrentTeb()->WOW32Reserved);
-    HANDLE16 oldDS = stack16->ds;
+    HANDLE16 oldDS = CURRENT_DS;
     WORD user = LoadLibrary16( "USER.EXE" );
     WORD gdi = LoadLibrary16( "GDI.EXE" );
-    stack16->ds = user;
+
+    CURRENT_DS = user;
     pHeapInfo->wUserFreePercent = (int)LocalCountFree16() * 100 / LocalHeapSize16();
-    stack16->ds = gdi;
+    CURRENT_DS = gdi;
     pHeapInfo->wGDIFreePercent  = (int)LocalCountFree16() * 100 / LocalHeapSize16();
-    stack16->ds = oldDS;
+    CURRENT_DS = oldDS;
     pHeapInfo->hUserSegment = user;
     pHeapInfo->hGDISegment  = gdi;
     FreeLibrary16( user );
diff --git a/dlls/user.exe16/message.c b/dlls/user.exe16/message.c
index e3ca3fd779d..ca90a31bfa6 100644
--- a/dlls/user.exe16/message.c
+++ b/dlls/user.exe16/message.c
@@ -2092,7 +2092,6 @@ static LRESULT combo_proc16( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam,
 
 static void edit_lock_buffer( HWND hwnd )
 {
-    STACK16FRAME* stack16 = MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved));
     HLOCAL16 hloc16 = GetWindowWord( hwnd, GWW_HANDLE16 );
     HANDLE16 oldDS;
     HLOCAL hloc32;
@@ -2101,8 +2100,8 @@ static void edit_lock_buffer( HWND hwnd )
     if (!hloc16) return;
     if (!(hloc32 = (HLOCAL)wow_handlers32.edit_proc( hwnd, EM_GETHANDLE, 0, 0, FALSE ))) return;
 
-    oldDS = stack16->ds;
-    stack16->ds = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
+    oldDS = CURRENT_DS;
+    CURRENT_DS = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
     size = LocalSize16(hloc16);
     if (LocalReAlloc( hloc32, size, LMEM_MOVEABLE ))
     {
@@ -2112,13 +2111,11 @@ static void edit_lock_buffer( HWND hwnd )
         LocalUnlock( hloc32 );
         LocalUnlock16( hloc16 );
     }
-    stack16->ds = oldDS;
-
+    CURRENT_DS = oldDS;
 }
 
 static void edit_unlock_buffer( HWND hwnd )
 {
-    STACK16FRAME* stack16 = MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved));
     HLOCAL16 hloc16 = GetWindowWord( hwnd, GWW_HANDLE16 );
     HANDLE16 oldDS;
     HLOCAL hloc32;
@@ -2128,8 +2125,8 @@ static void edit_unlock_buffer( HWND hwnd )
     if (!(hloc32 = (HLOCAL)wow_handlers32.edit_proc( hwnd, EM_GETHANDLE, 0, 0, FALSE ))) return;
     size = LocalSize( hloc32 );
 
-    oldDS = stack16->ds;
-    stack16->ds = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
+    oldDS = CURRENT_DS;
+    CURRENT_DS = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
     if (LocalReAlloc16( hloc16, size, LMEM_MOVEABLE ))
     {
         char *text = LocalLock( hloc32 );
@@ -2138,7 +2135,7 @@ static void edit_unlock_buffer( HWND hwnd )
         LocalUnlock( hloc32 );
         LocalUnlock16( hloc16 );
     }
-    stack16->ds = oldDS;
+    CURRENT_DS = oldDS;
 }
 
 static HLOCAL16 edit_get_handle( HWND hwnd )
@@ -2146,7 +2143,6 @@ static HLOCAL16 edit_get_handle( HWND hwnd )
     CHAR *textA;
     UINT alloc_size;
     HLOCAL hloc;
-    STACK16FRAME* stack16;
     HANDLE16 oldDS;
     HLOCAL16 hloc16 = GetWindowWord( hwnd, GWW_HANDLE16 );
 
@@ -2155,13 +2151,12 @@ static HLOCAL16 edit_get_handle( HWND hwnd )
     if (!(hloc = (HLOCAL)wow_handlers32.edit_proc( hwnd, EM_GETHANDLE, 0, 0, FALSE ))) return 0;
     alloc_size = LocalSize( hloc );
 
-    stack16 = MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved));
-    oldDS = stack16->ds;
-    stack16->ds = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
+    oldDS = CURRENT_DS;
+    CURRENT_DS = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
 
     if (!LocalHeapSize16())
     {
-        if (!LocalInit16(stack16->ds, 0, GlobalSize16(stack16->ds)))
+        if (!LocalInit16(CURRENT_DS, 0, GlobalSize16(CURRENT_DS)))
         {
             ERR("could not initialize local heap\n");
             goto done;
@@ -2187,15 +2182,14 @@ static HLOCAL16 edit_get_handle( HWND hwnd )
     SetWindowWord( hwnd, GWW_HANDLE16, hloc16 );
 
 done:
-    stack16->ds = oldDS;
+    CURRENT_DS = oldDS;
     return hloc16;
 }
 
 static void edit_set_handle( HWND hwnd, HLOCAL16 hloc16 )
 {
-    STACK16FRAME* stack16 = MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved));
     HINSTANCE16 hInstance = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
-    HANDLE16 oldDS = stack16->ds;
+    HANDLE16 oldDS = CURRENT_DS;
     HLOCAL hloc32;
     INT count;
     CHAR *text;
@@ -2203,7 +2197,7 @@ static void edit_set_handle( HWND hwnd, HLOCAL16 hloc16 )
     if (!(GetWindowLongW( hwnd, GWL_STYLE ) & ES_MULTILINE)) return;
     if (!hloc16) return;
 
-    stack16->ds = hInstance;
+    CURRENT_DS = hInstance;
     count = LocalSize16(hloc16);
     text = MapSL(LocalLock16(hloc16));
     if ((hloc32 = LocalAlloc(LMEM_MOVEABLE, count)))
@@ -2213,8 +2207,7 @@ static void edit_set_handle( HWND hwnd, HLOCAL16 hloc16 )
         LocalUnlock16(hloc16);
         SetWindowWord( hwnd, GWW_HANDLE16, hloc16 );
     }
-    stack16->ds = oldDS;
-
+    CURRENT_DS = oldDS;
     if (hloc32) wow_handlers32.edit_proc( hwnd, EM_SETHANDLE, (WPARAM)hloc32, 0, FALSE );
 }
 
@@ -2223,13 +2216,12 @@ static void edit_destroy_handle( HWND hwnd )
     HLOCAL16 hloc16 = GetWindowWord( hwnd, GWW_HANDLE16 );
     if (hloc16)
     {
-        STACK16FRAME* stack16 = MapSL(PtrToUlong(NtCurrentTeb()->WOW32Reserved));
-        HANDLE16 oldDS = stack16->ds;
+        HANDLE16 oldDS = CURRENT_DS;
 
-        stack16->ds = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
+        CURRENT_DS = GetWindowLongPtrW( hwnd, GWLP_HINSTANCE );
         while (LocalUnlock16(hloc16)) ;
         LocalFree16(hloc16);
-        stack16->ds = oldDS;
+        CURRENT_DS = oldDS;
         SetWindowWord( hwnd, GWW_HANDLE16, 0 );
     }
 }
diff --git a/dlls/user.exe16/user.c b/dlls/user.exe16/user.c
index 27b92793836..5063f9d2343 100644
--- a/dlls/user.exe16/user.c
+++ b/dlls/user.exe16/user.c
@@ -1394,11 +1394,10 @@ DWORD WINAPI GetTabbedTextExtent16( HDC16 hdc, LPCSTR lpstr, INT16 count,
  */
 DWORD WINAPI UserSeeUserDo16(WORD wReqType, WORD wParam1, WORD wParam2, WORD wParam3)
 {
-    STACK16FRAME* stack16 = MapSL((SEGPTR)NtCurrentTeb()->WOW32Reserved);
-    HANDLE16 oldDS = stack16->ds;
+    HANDLE16 oldDS = CURRENT_DS;
     DWORD ret = (DWORD)-1;
 
-    stack16->ds = USER_HeapSel;
+    CURRENT_DS = USER_HeapSel;
     switch (wReqType)
     {
     case USUD_LOCALALLOC:
@@ -1419,7 +1418,7 @@ DWORD WINAPI UserSeeUserDo16(WORD wReqType, WORD wParam1, WORD wParam2, WORD wPa
     default:
         WARN("wReqType %04x (unknown)\n", wReqType);
     }
-    stack16->ds = oldDS;
+    CURRENT_DS = oldDS;
     return ret;
 }
 
@@ -1787,32 +1786,31 @@ UINT16 WINAPI RealizePalette16( HDC16 hdc )
  */
 WORD WINAPI GetFreeSystemResources16( WORD resType )
 {
-    STACK16FRAME* stack16 = MapSL((SEGPTR)NtCurrentTeb()->WOW32Reserved);
-    HANDLE16 oldDS = stack16->ds;
+    HANDLE16 oldDS = CURRENT_DS;
     int userPercent, gdiPercent;
 
     switch(resType)
     {
     case GFSR_USERRESOURCES:
-        stack16->ds = USER_HeapSel;
+        CURRENT_DS = USER_HeapSel;
         userPercent = (int)LocalCountFree16() * 100 / LocalHeapSize16();
         gdiPercent  = 100;
-        stack16->ds = oldDS;
+        CURRENT_DS = oldDS;
         break;
 
     case GFSR_GDIRESOURCES:
-        stack16->ds = gdi_inst;
+        CURRENT_DS = gdi_inst;
         gdiPercent  = (int)LocalCountFree16() * 100 / LocalHeapSize16();
         userPercent = 100;
-        stack16->ds = oldDS;
+        CURRENT_DS = oldDS;
         break;
 
     case GFSR_SYSTEMRESOURCES:
-        stack16->ds = USER_HeapSel;
+        CURRENT_DS = USER_HeapSel;
         userPercent = (int)LocalCountFree16() * 100 / LocalHeapSize16();
-        stack16->ds = gdi_inst;
+        CURRENT_DS = gdi_inst;
         gdiPercent  = (int)LocalCountFree16() * 100 / LocalHeapSize16();
-        stack16->ds = oldDS;
+        CURRENT_DS = oldDS;
         break;
 
     default:
diff --git a/dlls/user.exe16/window.c b/dlls/user.exe16/window.c
index bf86719325b..5a9448a2131 100644
--- a/dlls/user.exe16/window.c
+++ b/dlls/user.exe16/window.c
@@ -456,8 +456,7 @@ HWND16 WINAPI GetParent16( HWND16 hwnd )
  */
 BOOL16 WINAPI IsWindow16( HWND16 hwnd )
 {
-    STACK16FRAME *frame = MapSL( (SEGPTR)NtCurrentTeb()->WOW32Reserved );
-    frame->es = USER_HeapSel;
+    CURRENT_STACK16->es = USER_HeapSel;
     /* don't use WIN_Handle32 here, we don't care about the full handle */
     return IsWindow( HWND_32(hwnd) );
 }
diff --git a/include/wine/winbase16.h b/include/wine/winbase16.h
index 5938ef19966..11ac4533736 100644
--- a/include/wine/winbase16.h
+++ b/include/wine/winbase16.h
@@ -23,6 +23,7 @@
 #include <windef.h>
 #include <winbase.h>
 #include <winnls.h>
+#include <winternl.h>
 #include <wine/windef16.h>
 
 #include <pshpack1.h>
@@ -561,4 +562,7 @@ BOOL16      WINAPI WritePrivateProfileSection16(LPCSTR,LPCSTR,LPCSTR);
 BOOL16      WINAPI WritePrivateProfileStruct16(LPCSTR,LPCSTR,LPVOID,UINT16,LPCSTR);
 BOOL16      WINAPI WriteProfileSection16(LPCSTR,LPCSTR);
 
+#define CURRENT_STACK16 ((STACK16FRAME *)MapSL((SEGPTR)NtCurrentTeb()->WOW32Reserved))
+#define CURRENT_DS      (CURRENT_STACK16->ds)
+
 #endif /* __WINE_WINE_WINBASE16_H */