diff --git a/mps/src/mpsw3.h b/mps/src/mpsw3.h
index 06393a2ed0c..73d39adb763 100644
--- a/mps/src/mpsw3.h
+++ b/mps/src/mpsw3.h
@@ -1,6 +1,6 @@
 /* impl.h.mpsw3: HARLEQUIN MEMORY POOL SYSTEM C INTERFACE, WINDOWS PART
  *
- * $HopeName: MMsrc!mpsw3.h(trunk.1) $
+ * $HopeName: MMsrc!mpsw3.h(trunk.2) $
  * Copyright (C) 1998 Harlequin Limited.  All rights reserved.
  *
  * .readership: customers, MPS developers.
@@ -26,7 +26,7 @@ extern void mps_SEH_handler(void *, size_t);
     mps_tramp_t _f = (f); \
     void *_p = (p); \
     size_t _s = (s); \
-    void *_hp; size_t _hs; \
+    void *_hp = NULL; size_t _hs = 0; \
     __try { \
       *_r_o = (*_f)(_p, _s); \
     } __except(mps_SEH_filter(GetExceptionInformation(), \