diff --git a/ChangeLog b/ChangeLog
index de57cf78d8..9c4836d61a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat Jun 22 13:43:00 2013  Charlie Somerville  <charliesome@ruby-lang.org>
+
+	* ext/etc/etc.c (etc_getpwnam): use PRIsVALUE in format string instead
+	  of %s and RSTRING_PTR
+
+	* ext/etc/etc.c (etc_getgrnam): ditto
+
 Sat Jun 22 13:07:15 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (CLEAR_LOWBITS): Rewritten without RSHIFTX.
diff --git a/ext/etc/etc.c b/ext/etc/etc.c
index 74a1fedbeb..de06c74947 100644
--- a/ext/etc/etc.c
+++ b/ext/etc/etc.c
@@ -183,7 +183,7 @@ etc_getpwnam(VALUE obj, VALUE nam)
 
     SafeStringValue(nam);
     pwd = getpwnam(RSTRING_PTR(nam));
-    if (pwd == 0) rb_raise(rb_eArgError, "can't find user for %s", RSTRING_PTR(nam));
+    if (pwd == 0) rb_raise(rb_eArgError, "can't find user for %"PRIsVALUE, nam);
     return setup_passwd(pwd);
 #else
     return Qnil;
@@ -426,7 +426,7 @@ etc_getgrnam(VALUE obj, VALUE nam)
 
     SafeStringValue(nam);
     grp = getgrnam(RSTRING_PTR(nam));
-    if (grp == 0) rb_raise(rb_eArgError, "can't find group for %s", RSTRING_PTR(nam));
+    if (grp == 0) rb_raise(rb_eArgError, "can't find group for %"PRIsVALUE, nam);
     return setup_group(grp);
 #else
     return Qnil;