Index: Modules/mmapmodule.c
===================================================================
--- Modules/mmapmodule.c	(revision 73839)
+++ Modules/mmapmodule.c	(working copy)
@@ -323,20 +323,33 @@
 static int
 is_writeable(mmap_object *self)
 {
-	if (self->access != ACCESS_READ)
-		return 1;
-	PyErr_Format(PyExc_TypeError, "mmap can't modify a readonly memory map.");
-	return 0;
+	if (self->access == ACCESS_READ) {
+		PyErr_Format(PyExc_TypeError, "mmap can't modify a readonly memory map");
+		return 0;
+	}
+	return 1;
 }
 
 static int
 is_resizeable(mmap_object *self)
 {
-	if ((self->access == ACCESS_WRITE) || (self->access == ACCESS_DEFAULT))
-		return 1;
-	PyErr_Format(PyExc_TypeError,
-		     "mmap can't resize a readonly or copy-on-write memory map.");
-	return 0;
+	if ((self->access != ACCESS_WRITE) && (self->access != ACCESS_DEFAULT)) {
+		PyErr_Format(PyExc_TypeError,
+			     "mmap can't resize a readonly or copy-on-write memory map");
+		return 0;
+	}
+#if defined(MS_WINDOWS)
+	if (self->file_handle == INVALID_HANDLE_VALUE) {
+		PyErr_Format(PyExc_TypeError, "mmap can't resize an anonymous memory map");
+		return 0;
+	}
+#elif defined(UNIX)
+	if (self->fd == -1) {
+		PyErr_Format(PyExc_TypeError, "mmap can't resize an anonymous memory map");
+		return 0;
+	}
+#endif
+	return 1;
 }