diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2dc86bd..19310b31 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 Version XXX:
 
+* Fix reuse of sliding window in WebSocket permessage_deflate.
 * Fix accept error handling in http_server_async example.
 * Move library-specific docca configuration to Beast.
 * Remove dependency on RTTI in `test::stream`.
diff --git a/include/boost/beast/websocket/detail/impl_base.hpp b/include/boost/beast/websocket/detail/impl_base.hpp
index fc5bf0bc..00912998 100644
--- a/include/boost/beast/websocket/detail/impl_base.hpp
+++ b/include/boost/beast/websocket/detail/impl_base.hpp
@@ -137,7 +137,7 @@ struct impl_base<true>
                     return false;
                 if(zs.avail_out >= 6)
                 {
-                    zo.write(zs, zlib::Flush::full, ec);
+                    zo.write(zs, zlib::Flush::sync, ec);
                     BOOST_ASSERT(! ec);
                     // remove flush marker
                     zs.total_out -= 4;