diff --git a/cups-str3312.patch b/cups-str3312.patch
new file mode 100644
index 0000000..f6445d0
--- /dev/null
+++ b/cups-str3312.patch
@@ -0,0 +1,40 @@
+diff -up cups-1.4rc1/cgi-bin/admin.c.str3312 cups-1.4rc1/cgi-bin/admin.c
+--- cups-1.4rc1/cgi-bin/admin.c.str3312	2009-05-11 22:21:29.000000000 +0100
++++ cups-1.4rc1/cgi-bin/admin.c	2009-08-27 16:33:00.691275487 +0100
+@@ -628,6 +628,15 @@ do_am_class(http_t *http,		/* I - HTTP c
+     return;
+   }
+ 
++  if (!name)
++    {
++      cgiSetVariable("ERROR", cgiText(_("Missing form variable!")));
++      cgiStartHTML(title);
++      cgiCopyTemplateLang("error.tmpl");
++      cgiEndHTML();
++      return;
++    }
++
+   for (ptr = name; *ptr; ptr ++)
+     if ((*ptr >= 0 && *ptr <= ' ') || *ptr == 127 || *ptr == '/' || *ptr == '#')
+       break;
+@@ -662,8 +671,7 @@ do_am_class(http_t *http,		/* I - HTTP c
+   request = ippNewRequest(CUPS_ADD_CLASS);
+ 
+   httpAssembleURIf(HTTP_URI_CODING_ALL, uri, sizeof(uri), "ipp", NULL,
+-                   "localhost", 0, "/classes/%s",
+-		   cgiGetVariable("PRINTER_NAME"));
++                   "localhost", 0, "/classes/%s", name);
+   ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_URI, "printer-uri",
+                NULL, uri);
+ 
+diff -up cups-1.4rc1/templates/modify-class.tmpl.str3312 cups-1.4rc1/templates/modify-class.tmpl
+--- cups-1.4rc1/templates/modify-class.tmpl.str3312	2008-09-20 04:33:59.000000000 +0100
++++ cups-1.4rc1/templates/modify-class.tmpl	2009-08-27 16:33:00.693275103 +0100
+@@ -4,6 +4,7 @@
+ 
+ <FORM METHOD="POST" ACTION="/admin">
+ <INPUT TYPE="HIDDEN" NAME="OP" VALUE="{op}">
++<INPUT TYPE="HIDDEN" NAME="PRINTER_NAME" VALUE="{printer_name}">
+ 
+ <TABLE>
+ <TR>
diff --git a/cups.spec b/cups.spec
index c29ff5b..9d94a75 100644
--- a/cups.spec
+++ b/cups.spec
@@ -10,7 +10,7 @@
 Summary: Common Unix Printing System
 Name: cups
 Version: 1.4
-Release: 0.%{pre}.19%{?dist}
+Release: 0.%{pre}.20%{?dist}
 License: GPLv2
 Group: System Environment/Daemons
 Source: ftp://ftp.easysw.com/pub/cups/test//cups-%{version}%{?pre}%{?svn}-source.tar.bz2
@@ -71,6 +71,7 @@ Patch43: cups-str3292.patch
 Patch44: cups-str3293.patch
 Patch45: cups-str3308.patch
 Patch46: cups-str3311.patch
+Patch47: cups-str3312.patch
 Patch100: cups-lspp.patch
 Epoch: 1
 Url: http://www.cups.org/
@@ -242,6 +243,7 @@ module.
 %patch44 -p1 -b .str3293
 %patch45 -p1 -b .str3308
 %patch46 -p1 -b .str3311
+%patch47 -p1 -b .str3312
 
 %if %lspp
 %patch100 -p1 -b .lspp
@@ -536,6 +538,10 @@ rm -rf $RPM_BUILD_ROOT
 %{php_extdir}/phpcups.so
 
 %changelog
+* Wed Aug 26 2009 Tim Waugh <twaugh@redhat.com> 1:1.4-0.rc1.20
+- Fixed admin.cgi crash when modifying a class (bug #519724,
+  STR #3312, patch from Jiri Popelka).
+
 * Wed Aug 26 2009 Tim Waugh <twaugh@redhat.com> 1:1.4-0.rc1.19
 - Prevent infinite loop in cupsDoIORequest when processing HTTP
   errors (bug #518065, bug #519663, STR #3311).