diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bd31f3e27bad..b71a509ceb83 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2007-04-20  Richard Henderson  <rth@redhat.com>
+
+        * config/alpha/linux.h (CPP_SPEC): Undef before redefine.
+
 2007-04-20  Bernd Schmidt  <bernd.schmidt@analog.com>
 
 	* reload.c (combine_reloads): When trying to use a dying register,
diff --git a/gcc/config/alpha/linux.h b/gcc/config/alpha/linux.h
index 5583922efa66..1be120f9e2b8 100644
--- a/gcc/config/alpha/linux.h
+++ b/gcc/config/alpha/linux.h
@@ -44,6 +44,7 @@ Boston, MA 02110-1301, USA.  */
    %{shared:-lc} \
    %{!shared: %{profile:-lc_p}%{!profile:-lc}}"
 
+#undef CPP_SPEC
 #define CPP_SPEC "%{posix:-D_POSIX_SOURCE} %{pthread:-D_REENTRANT}"
 
 /* Show that we need a GP when profiling.  */