diff -up webkit-1.3.1/JavaScriptCore/wtf/Platform.h.s390 webkit-1.3.1/JavaScriptCore/wtf/Platform.h
--- webkit-1.3.1/JavaScriptCore/wtf/Platform.h.s390	2010-05-24 15:53:11.000000000 +0200
+++ webkit-1.3.1/JavaScriptCore/wtf/Platform.h	2010-06-14 15:24:18.000000000 +0200
@@ -178,6 +178,18 @@
 #define WTF_CPU_SPARC 1
 #endif
 
+/* CPU(S390X) - S390 64-bit */
+#if defined(__s390x__)
+#define WTF_CPU_S390X 1
+#define WTF_CPU_BIG_ENDIAN 1
+#endif
+
+/* CPU(S390) - S390 32-bit */
+#if defined(__s390__)
+#define WTF_CPU_S390 1
+#define WTF_CPU_BIG_ENDIAN 1
+#endif
+
 /* CPU(X86) - i386 / x86 32-bit */
 #if   defined(__i386__) \
     || defined(i386)     \
@@ -899,6 +911,7 @@
 #if (CPU(X86_64) && (OS(UNIX) || OS(WINDOWS))) \
     || (CPU(IA64) && !CPU(IA64_32)) \
     || CPU(ALPHA) \
+    || CPU(S390X) \
     || CPU(SPARC64)
 #define WTF_USE_JSVALUE64 1
 #elif CPU(ARM) || CPU(PPC64) || CPU(MIPS)