diff -uriwb misc/build/icu.old/source/aclocal.m4 misc/build/icu/source/aclocal.m4
--- misc/build/icu.old/source/aclocal.m4	2012-04-05 21:49:28.000000000 +0100
+++ misc/build/icu/source/aclocal.m4	2012-06-21 15:44:57.299256932 +0100
@@ -455,7 +455,7 @@
             case "${host}" in
             *-*-solaris*)
                 CFLAGS="$CFLAGS -Wall -ansi -pedantic -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -Wno-long-long"
-                CFLAGS="$CFLAGS -D__STDC__=0";;
+                CFLAGS="$CFLAGS -std=c99";;
             *-*-hpux*)
                 echo "# Note: We are not using '-ansi' with HP/UX GCC because int64_t broke, see <http://bugs.icu-project.org/trac/ticket/8493>"
                 CFLAGS="$CFLAGS -Wall -pedantic -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -Wno-long-long";;
@@ -474,10 +474,6 @@
         if test "$GXX" = yes
         then
             CXXFLAGS="$CXXFLAGS -W -Wall -ansi -pedantic -Wpointer-arith -Wwrite-strings -Wno-long-long"
-            case "${host}" in
-            *-*-solaris*)
-                CXXFLAGS="$CXXFLAGS -D__STDC__=0";;
-            esac
         else
             case "${host}" in
             *-*-cygwin)
diff -uriwb misc/build/icu.old/source/common/uposixdefs.h misc/build/icu/source/common/uposixdefs.h
--- misc/build/icu.old/source/common/uposixdefs.h	2012-04-05 21:46:18.000000000 +0100
+++ misc/build/icu/source/common/uposixdefs.h	2012-06-21 15:45:17.613369477 +0100
@@ -52,7 +52,7 @@
  *
  * z/OS needs this definition for timeval and to get usleep.
  */
-#if !defined(_XOPEN_SOURCE_EXTENDED)
+#if !defined(_XOPEN_SOURCE_EXTENDED) && (defined(__IBMC__) || defined(__IBMCPP__))
 #   define _XOPEN_SOURCE_EXTENDED 1
 #endif
 
diff -uriwb misc/build/icu.old/source/configure misc/build/icu/source/configure
--- misc/build/icu.old/source/configure	2012-04-05 21:49:28.000000000 +0100
+++ misc/build/icu/source/configure	2012-06-21 15:44:42.817030445 +0100
@@ -4264,7 +4264,7 @@
             case "${host}" in
             *-*-solaris*)
                 CFLAGS="$CFLAGS -Wall -ansi -pedantic -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -Wno-long-long"
-                CFLAGS="$CFLAGS -D__STDC__=0";;
+                CFLAGS="$CFLAGS -std=c99";;
             *-*-hpux*)
                 echo "# Note: We are not using '-ansi' with HP/UX GCC because int64_t broke, see <http://bugs.icu-project.org/trac/ticket/8493>"
                 CFLAGS="$CFLAGS -Wall -pedantic -Wshadow -Wpointer-arith -Wmissing-prototypes -Wwrite-strings -Wno-long-long";;
@@ -4283,10 +4283,6 @@
         if test "$GXX" = yes
         then
             CXXFLAGS="$CXXFLAGS -W -Wall -ansi -pedantic -Wpointer-arith -Wwrite-strings -Wno-long-long"
-            case "${host}" in
-            *-*-solaris*)
-                CXXFLAGS="$CXXFLAGS -D__STDC__=0";;
-            esac
         else
             case "${host}" in
             *-*-cygwin)