diff -r 355af3657df3 Modules/zipimport.c
--- a/Modules/zipimport.c	Wed Dec 04 09:43:21 2013 +0100
+++ b/Modules/zipimport.c	Wed Dec 04 10:30:16 2013 +0100
@@ -903,13 +903,19 @@
     arc_offset = header_position - header_offset - header_size;
     header_offset += arc_offset;
 
+    if (header_offset > LONG_MAX) {
+        fclose(fp);
+        PyErr_Format(ZipImportError, "can't read Zip file: %R", archive);
+        return NULL;
+    }
+
     files = PyDict_New();
     if (files == NULL)
         goto error;
 
     /* Start of Central Directory */
     count = 0;
-    if (fseek(fp, header_offset, 0) == -1)
+    if (fseek(fp, (long)header_offset, 0) == -1)
         goto file_error;
     for (;;) {
         PyObject *t;