diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e77c144bd0a..0707924a77d 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2006-06-13  Roger Sayle  <roger@eyesopen.com>
+
+	* configure.ac (HAS_MCONTEXT_T_UNDERSCORES): Include <sys/signal.h>
+	before <ucontext.h> to define sigset_t required by <sys/ucontext.h>.
+	* configure: Regenerate.
+
 2006-06-13  Jie Zhang  <jie.zhang@analog.com>
 
 	* config/bfin/bfin.c (bfin_reorg_loops): Only call recog_memoized ()
diff --git a/gcc/configure b/gcc/configure
index d170a3afecb..43d5fe53816 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -12289,6 +12289,7 @@ if test "${gcc_cv_mcontext_underscores+set}" = set; then
 else
   cat >conftest.$ac_ext <<_ACEOF
 
+#include <sys/signal.h>
 #include <ucontext.h>
 int main() { mcontext_t m; if (m->ss.srr0) return 0; return 0; }
 
diff --git a/gcc/configure.ac b/gcc/configure.ac
index a51f4807dff..7ef1f4e5b4f 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -1348,6 +1348,7 @@ case ${host} in
     AC_CACHE_CHECK([whether mcontext_t fields have underscores],
       gcc_cv_mcontext_underscores,
       AC_COMPILE_IFELSE([
+#include <sys/signal.h>
 #include <ucontext.h>
 int main() { mcontext_t m; if (m->ss.srr0) return 0; return 0; }
 ],