diff --git a/ChangeLog b/ChangeLog
index 0c6b43ebc0..83a28dbb2f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2018-11-01  Joseph Myers  <joseph@codesourcery.com>
 
+	* posix/bug-regex22.c (main): Use puts with distinct error
+	messages for unexpected success of re_compile_pattern, not printf
+	with NULL argument to %s.
+
 	* stdio-common/bug22.c: Include <libc-diag.h>.
 	(do_test): Disable -Wformat-overflow= warnings around fprintf
 	calls outputting more than INT_MAX characters.
diff --git a/posix/bug-regex22.c b/posix/bug-regex22.c
index 2c561d8e43..73b222cbff 100644
--- a/posix/bug-regex22.c
+++ b/posix/bug-regex22.c
@@ -99,8 +99,8 @@ main (void)
   s = re_compile_pattern ("[[:DIGIT:]]", 11, &re);
   if (s == NULL)
     {
-      printf ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: %s\n",
-	      s);
+      puts ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: "
+	    "length 11");
       result = 1;
     }
 
@@ -109,8 +109,8 @@ main (void)
   s = re_compile_pattern ("[[:DIGIT:]]", 2, &re);
   if (s == NULL)
     {
-      printf ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: %s\n",
-	      s);
+      puts ("compilation of \"[[:DIGIT:]]\" pattern unexpectedly succeeded: "
+	    "length 2");
       result = 1;
     }