--- a/pr/include/private/primpl.h
+++ b/pr/include/private/primpl.h
@@ -1340,17 +1340,17 @@ struct PRSem {
     PRInt8 notused;
 #endif
 };
 
 /*************************************************************************/
 
 struct PRStackStr {
     /* head MUST be at offset 0; assembly language code relies on this */
-#if defined(AIX) || defined(OSF1)
+#if defined(AIX)
     volatile PRStackElem prstk_head;
 #else
     PRStackElem prstk_head;
 #endif
 
     PRLock *prstk_lock;
     char *prstk_name;
 };