Index: Lib/test/test_mmap.py
===================================================================
--- Lib/test/test_mmap.py	(revision 69718)
+++ Lib/test/test_mmap.py	(working copy)
@@ -348,6 +348,24 @@
             m[x] = ch = chr(x & 255)
             self.assertEqual(m[x], ch)
 
+    def test_anonymous_resize(self):
+        RESIZE = 2 * PAGESIZE
+        m = mmap.mmap(-1, PAGESIZE)
+        try:
+            m.resize(RESIZE)
+        except SystemError:
+            # resize() not supported
+            # No messages are printed, since the output of this test suite
+            # would then be different across platforms.
+            pass
+        else:
+            # resize() is supported
+            self.assertEqual(len(m), RESIZE)
+            # Check that we can no longer seek beyond the new size.
+            self.assertRaises(ValueError, m.seek, 1+RESIZE, 0)
+        finally:
+            m.close()
+
     def test_extended_getslice(self):
         # Test extended slicing by comparing with list slicing.
         s = "".join(chr(c) for c in reversed(range(256)))
Index: Modules/mmapmodule.c
===================================================================
--- Modules/mmapmodule.c	(revision 69718)
+++ Modules/mmapmodule.c	(working copy)
@@ -448,17 +448,20 @@
 		off_hi = 0;
 		off_lo = (DWORD)self->offset;
 #endif
-		SetFilePointer(self->file_handle,
-			       newSizeLow, &newSizeHigh, FILE_BEGIN);
-		/* Change the size of the file */
-		SetEndOfFile(self->file_handle);
+		if (self->file_handle != INVALID_HANDLE_VALUE) {
+			DWORD copySizeHigh = newSizeHigh;
+			SetFilePointer(self->file_handle,
+				       newSizeLow, &copySizeHigh, FILE_BEGIN);
+			/* Change the size of the file */
+			SetEndOfFile(self->file_handle);
+		}
 		/* Create another mapping object and remap the file view */
 		self->map_handle = CreateFileMapping(
 			self->file_handle,
 			NULL,
 			PAGE_READWRITE,
-			0,
-			0,
+			newSizeHigh,
+			newSizeLow,
 			self->tagname);
 		if (self->map_handle != NULL) {
 			self->data = (char *) MapViewOfFile(self->map_handle,