diff -up Ice-3.4.0/cpp/include/IceUtil/Config.h.s390 Ice-3.4.0/cpp/include/IceUtil/Config.h
--- Ice-3.4.0/cpp/include/IceUtil/Config.h.s390	2010-06-20 10:57:34.000000000 +0200
+++ Ice-3.4.0/cpp/include/IceUtil/Config.h	2010-06-20 10:59:38.000000000 +0200
@@ -26,7 +26,7 @@
 #   define ICE_LITTLE_ENDIAN
 #elif defined(__sparc) || defined(__sparc__) || defined(__hppa)      || \
       defined(__ppc__) || defined(__powerpc) || defined(_ARCH_COM) || \
-      defined(__MIPSEB__) || (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN))
+      defined(__MIPSEB__) || defined(__s390__) || (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN))
 #   define ICE_BIG_ENDIAN
 #else
 #   error "Unknown architecture"
@@ -42,7 +42,7 @@
 //
 #   define  ICE_32
 #elif defined(__sun) && (defined(__sparcv9) || defined(__x86_64))  || \
-      defined(__linux) && defined(__x86_64)                        || \
+      defined(__linux) && (defined(__x86_64) || defined(__s390x__)) || \
       defined(__hppa) && defined(__LP64__)                         || \
       defined(_ARCH_COM) && defined(__64BIT__)                     || \
       defined(__alpha__)                                           || \