diff --git a/ACE/ace/config-macosx-leopard.h b/ACE/ace/config-macosx-leopard.h
index f89be4ae67ecf..3bb2f73a9918b 100644
--- a/ACE/ace/config-macosx-leopard.h
+++ b/ACE/ace/config-macosx-leopard.h
@@ -16,7 +16,7 @@
 #endif /* ! __ACE_INLINE__ */
 
 #if !defined (ACE_SIZEOF_LONG_DOUBLE)
-#  define ACE_SIZEOF_LONG_DOUBLE 16
+#  define ACE_SIZEOF_LONG_DOUBLE __SIZEOF_LONG_DOUBLE__
 #endif // ACE_SIZEOF_LONG_DOUBLE
 
 #if defined (__GNUG__)
diff --git a/ACE/ace/config-macosx-tiger.h b/ACE/ace/config-macosx-tiger.h
index 0bbfd63238b99..88fe5c24f8c1e 100644
--- a/ACE/ace/config-macosx-tiger.h
+++ b/ACE/ace/config-macosx-tiger.h
@@ -9,7 +9,7 @@
 #endif /* ! __ACE_INLINE__ */
 
 #if !defined (ACE_SIZEOF_LONG_DOUBLE)
-#  define ACE_SIZEOF_LONG_DOUBLE 16
+#  define ACE_SIZEOF_LONG_DOUBLE __SIZEOF_LONG_DOUBLE__
 #endif // ACE_SIZEOF_LONG_DOUBLE
 
 #if defined (__GNUG__)