diff --git a/Misc/NEWS b/Misc/NEWS
index 03cd7dff327..f5275b8cc4d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -610,6 +610,9 @@ Extension Modules
 
 - Issue #2389: Array objects are now pickled in a portable manner.
 
+- Expat: Fix DoS via XML document with malformed UTF-8 sequences
+  (CVE_2009_3560).
+
 Build
 -----
 
diff --git a/Modules/expat/xmlparse.c b/Modules/expat/xmlparse.c
index e04426d0cc1..105958b6496 100644
--- a/Modules/expat/xmlparse.c
+++ b/Modules/expat/xmlparse.c
@@ -3682,6 +3682,9 @@ doProlog(XML_Parser parser,
         return XML_ERROR_UNCLOSED_TOKEN;
       case XML_TOK_PARTIAL_CHAR:
         return XML_ERROR_PARTIAL_CHAR;
+      case -XML_TOK_PROLOG_S:
+        tok = -tok;
+        break;
       case XML_TOK_NONE:
 #ifdef XML_DTD
         /* for internal PE NOT referenced between declarations */