diff --git a/CHANGELOG b/CHANGELOG
index 2e3e4b1..4ebeb5a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,7 @@
+2020-03-23
+    - 2.13.3
+    - [BUGFIX] ACK ping-pong: TIMESTAMP frame is not to be acked.
+
 2020-03-13
     - 2.13.2
     - [BUGFIX] Use of new lsxpack_header API's hsi_prepare_decode().
diff --git a/docs/conf.py b/docs/conf.py
index cb0138f..4e8cb0c 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -26,7 +26,7 @@ author = u'LiteSpeed Technologies'
 # The short X.Y version
 version = u'2.13'
 # The full version, including alpha/beta/rc tags
-release = u'2.13.2'
+release = u'2.13.3'
 
 
 # -- General configuration ---------------------------------------------------
diff --git a/include/lsquic.h b/include/lsquic.h
index bcbd74b..f793f8f 100644
--- a/include/lsquic.h
+++ b/include/lsquic.h
@@ -25,7 +25,7 @@ extern "C" {
 
 #define LSQUIC_MAJOR_VERSION 2
 #define LSQUIC_MINOR_VERSION 13
-#define LSQUIC_PATCH_VERSION 2
+#define LSQUIC_PATCH_VERSION 3
 
 /**
  * Engine flags:
diff --git a/src/liblsquic/lsquic_packet_common.h b/src/liblsquic/lsquic_packet_common.h
index 5f2bd1b..54c80ad 100644
--- a/src/liblsquic/lsquic_packet_common.h
+++ b/src/liblsquic/lsquic_packet_common.h
@@ -227,7 +227,7 @@ extern const char *const lsquic_pns2str[];
 /* [draft-ietf-quic-transport-24] Section 1.2 */
 #define IQUIC_FRAME_ACKABLE_MASK (  \
     ALL_IQUIC_FRAMES & ~(QUIC_FTBIT_ACK|QUIC_FTBIT_PADDING\
-                                            |QUIC_FTBIT_CONNECTION_CLOSE))
+                            |QUIC_FTBIT_CONNECTION_CLOSE|QUIC_FTBIT_TIMESTAMP))
 
 /* [draft-ietf-quic-transport-20], Section 13.2 */
 /* We bend some rules and retransmit BLOCKED, MAX_DATA, MAX_STREAM_DATA,