diff --git a/ChangeLog b/ChangeLog
index db1eea3..4347dcb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2006-11-04  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* src/sdiff.c (sigprocmask) [! HAVE_SIGPROCMASK]: Cast 2nd arg to
+	sigset_t *, since it might be a literal 0.  Problem reported by
+	Paul Edwards for MVS 3.8.
+
 2006-09-05  Paul Eggert  <eggert@cs.ucla.edu>
 
 	* NEWS: diff -u no longer outputs trailing white space unless the
diff --git a/src/sdiff.c b/src/sdiff.c
index 6ad4949..8f53762 100644
--- a/src/sdiff.c
+++ b/src/sdiff.c
@@ -112,7 +112,9 @@ static int const sigs[] = {
 #  define SIG_SETMASK (! SIG_BLOCK)
 # endif
 # define sigprocmask(how, n, o) \
-    ((how) == SIG_BLOCK ? *(o) = sigblock (*(n)) : sigsetmask (*(n)))
+    ((how) == SIG_BLOCK \
+     ? *(sigset_t *) (o) = sigblock (*(n)) \
+     : sigsetmask (*(n)))
 #endif
 
 static bool diraccess (char const *);