diff --git a/mysql-test/suite/binlog/r/binlog_gtid_mix_ok_packet_all_gtids.result b/mysql-test/suite/binlog/r/binlog_gtid_mix_ok_packet_all_gtids.result
new file mode 100644
index 000000000000..3f50d49dd6ac
--- /dev/null
+++ b/mysql-test/suite/binlog/r/binlog_gtid_mix_ok_packet_all_gtids.result
@@ -0,0 +1,46 @@
+# ALL_GTIDS at startup: this must return GTID:1
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1
+
+# ALL_GTIDS at startup: this must return GTID:1-2
+DROP TABLE t1;
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-2
+
+## ALL_GTIDS -> ALL_GTIDS : this must return GTID:1-2 ##
+SET SESSION session_track_gtids='ALL_GTIDS';
+SET SESSION session_track_gtids='ALL_GTIDS';
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-2
+
+## ALL_GTIDS -> OWN_GTID: this must return GTID:1-2 ##
+SET SESSION session_track_gtids='ALL_GTIDS';
+SET SESSION session_track_gtids='OWN_GTID';
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-2
+
+## ALL_GTIDS -> OFF : this must return GTID:1-2 ##
+SET SESSION session_track_gtids='ALL_GTIDS';
+SET SESSION session_track_gtids='OFF';
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-2
+
+## OWN_GTID -> ALL_GTIDS : this must return '' ##
+SET SESSION session_track_gtids='OWN_GTID';
+SET SESSION session_track_gtids='ALL_GTIDS';
+## OWN_GTID -> OWN_GTID: this must return '' ##
+SET SESSION session_track_gtids='OWN_GTID';
+SET SESSION session_track_gtids='OWN_GTID';
+## OWN_GTID -> OFF : this must return '' ##
+SET SESSION session_track_gtids='OWN_GTID';
+SET SESSION session_track_gtids='OFF';
+## OFF -> ALL_GTIDS : this must return '' ##
+SET SESSION session_track_gtids='OFF';
+SET SESSION session_track_gtids='ALL_GTIDS';
+## OFF -> OWN_GTID: this must return '' ##
+SET SESSION session_track_gtids='OFF';
+SET SESSION session_track_gtids='OWN_GTID';
+## OFF -> OFF : this must return '' ##
+SET SESSION session_track_gtids='OFF';
+SET SESSION session_track_gtids='OFF';
diff --git a/mysql-test/suite/binlog/r/binlog_gtid_mix_response_packet.result b/mysql-test/suite/binlog/r/binlog_gtid_mix_response_packet.result
index 86c850ca2006..c7d06f564ff9 100644
--- a/mysql-test/suite/binlog/r/binlog_gtid_mix_response_packet.result
+++ b/mysql-test/suite/binlog/r/binlog_gtid_mix_response_packet.result
@@ -1,3 +1,30 @@
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+DROP TABLE t1;
+set session session_track_gtids='own_gtid';
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:3
+
+INSERT INTO t1 VALUES (1);
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:4
+
+set session session_track_gtids='all_gtids';
+SELECT * FROM t1;
+c1
+1
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-4
+
+DROP TABLE t1;
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-5
+
+set session session_track_gtids='off';
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-5
+
+RESET MASTER;
 SELECT @@server_uuid;
 @@server_uuid
 00000000-1111-0000-1111-000000000000
@@ -13,10 +40,6 @@ CREATE TABLE t2 (c1 INT) Engine=InnoDB;
 
 SET SESSION GTID_NEXT=AUTOMATIC;
 SET SESSION SESSION_TRACK_GTIDS=ALL_GTIDS;
--- Tracker : SESSION_TRACK_GTIDS
--- 11111111-aaaa-2222-bbbb-000000000000:1,
-11111111-aaaa-2222-bbbb-111111111111:1
-
 CREATE TABLE t3 (c1 INT) Engine=InnoDB;
 -- Tracker : SESSION_TRACK_GTIDS
 -- 00000000-1111-0000-1111-000000000000:1,
@@ -71,6 +94,9 @@ DROP TABLE t1, t2;
 -- 00000000-1111-0000-1111-000000000000:1-6
 
 SET SESSION SESSION_TRACK_GTIDS=OWN_GTID;
+-- Tracker : SESSION_TRACK_GTIDS
+-- 00000000-1111-0000-1111-000000000000:1-6
+
 RESET MASTER;
 CREATE TABLE t1 (c1 INT) Engine=InnoDB;
 -- Tracker : SESSION_TRACK_GTIDS
diff --git a/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids-master.opt b/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids-master.opt
new file mode 100644
index 000000000000..901f4b99d1d4
--- /dev/null
+++ b/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids-master.opt
@@ -0,0 +1 @@
+--log-slave-updates --enforce-gtid-consistency --gtid-mode=ON --debug=+d,server_uuid_deterministic --session-track-gtids=ALL_GTIDS
diff --git a/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids.test b/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids.test
new file mode 100644
index 000000000000..da5f0c5213e4
--- /dev/null
+++ b/mysql-test/suite/binlog/t/binlog_gtid_mix_ok_packet_all_gtids.test
@@ -0,0 +1,71 @@
+--source include/have_binlog_format_mixed.inc
+--source include/have_gtid.inc
+--source include/have_debug.inc
+
+# BUG#19667258: WL#6972 - SERVER CRASH ON SET SESSION SESSION_TRACK_GTIDS='OFF'
+
+# This test file is configured to start the server with:
+#
+#  --session_track_gtids='ALL_GTIDS'
+#
+# Then we are looking to assert the following:
+# - Verify that the following statements include
+#   GTID data in the OK packet immediately after start
+#   the server starts up.
+# - Verify that every transition includes the expected
+#   GTID data in the OK packet.
+
+--enable_session_track_info
+
+--echo # ALL_GTIDS at startup: this must return GTID:1
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+
+--echo # ALL_GTIDS at startup: this must return GTID:1-2
+DROP TABLE t1;
+
+--disable_session_track_info
+
+--let $i=3
+while($i)
+{
+  if ($i==3)
+  {
+    --let $from=ALL_GTIDS
+  }
+
+  if ($i==2)
+  {
+    --let $from=OWN_GTID
+  }
+
+  if ($i==1)
+  {
+    --let $from=OFF
+  }
+  
+  --let $text= this must return ''
+  if (`SELECT '$from' = 'ALL_GTIDS'`)
+  {
+    --let $text= this must return GTID:1-2
+  }
+
+  --echo ## $from -> ALL_GTIDS : $text ##
+  --eval SET SESSION session_track_gtids='$from'
+  --enable_session_track_info
+  SET SESSION session_track_gtids='ALL_GTIDS';
+  --disable_session_track_info
+
+  --echo ## $from -> OWN_GTID: $text ##
+  --eval SET SESSION session_track_gtids='$from'
+  --enable_session_track_info
+  SET SESSION session_track_gtids='OWN_GTID';
+  --disable_session_track_info
+
+  --echo ## $from -> OFF : $text ##
+  --eval SET SESSION session_track_gtids='$from'
+  --enable_session_track_info
+  SET SESSION session_track_gtids='OFF';
+  --disable_session_track_info
+
+  --dec $i
+}
diff --git a/mysql-test/suite/binlog/t/binlog_gtid_mix_response_packet.test b/mysql-test/suite/binlog/t/binlog_gtid_mix_response_packet.test
index a0ffe5121c37..d96c4d73d0a7 100644
--- a/mysql-test/suite/binlog/t/binlog_gtid_mix_response_packet.test
+++ b/mysql-test/suite/binlog/t/binlog_gtid_mix_response_packet.test
@@ -8,6 +8,21 @@
 # need debug build to be able to set a deterministic server uuid
 --source include/have_debug.inc
 
+# BUG#19667258: WL#6972 - SERVER CRASH ON SET SESSION SESSION_TRACK_GTIDS='OFF'
+
+--enable_session_track_info
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+DROP TABLE t1;
+set session session_track_gtids='own_gtid';
+CREATE TABLE t1 (c1 INT) Engine=InnoDB;
+INSERT INTO t1 VALUES (1);
+set session session_track_gtids='all_gtids';
+SELECT * FROM t1;
+DROP TABLE t1;
+set session session_track_gtids='off';
+RESET MASTER;
+--disable_session_track_info
+
 ########################################################
 # Sanity Test.
 #
diff --git a/sql/rpl_context.cc b/sql/rpl_context.cc
index cbddf93248b7..1364193bf13b 100644
--- a/sql/rpl_context.cc
+++ b/sql/rpl_context.cc
@@ -55,7 +55,7 @@ bool Session_consistency_gtids_ctx::notify_after_transaction_commit(const THD* t
   if (!shall_collect(thd))
     DBUG_RETURN(res);
 
-  if (thd->variables.session_track_gtids == ALL_GTIDS)
+  if (m_curr_session_track_gtids == ALL_GTIDS)
   {
     /*
      If one is configured to read all writes, we always collect
@@ -84,7 +84,7 @@ bool Session_consistency_gtids_ctx::notify_after_gtid_executed_update(const THD
   if (!shall_collect(thd))
     DBUG_RETURN(res);
 
-  if (thd->variables.session_track_gtids == OWN_GTID)
+  if (m_curr_session_track_gtids == OWN_GTID)
   {
     const Gtid& gtid= thd->owned_gtid;
     if (gtid.sidno == -1) // we need to add thd->owned_gtid_set
@@ -131,12 +131,19 @@ bool Session_consistency_gtids_ctx::notify_after_response_packet(const THD *thd)
   if (m_gtid_set && !m_gtid_set->is_empty())
     m_gtid_set->clear();
 
+  /*
+   Every time we get a notification that a packet was sent, we update 
+   this value. It may have changed (the previous command may have been
+   a SET SESSION session_track_gtids=...;).
+   */
+  m_curr_session_track_gtids= thd->variables.session_track_gtids;
   DBUG_RETURN(res);
 }
 
 void
 Session_consistency_gtids_ctx::register_ctx_change_listener(
-              Session_consistency_gtids_ctx::Ctx_change_listener* listener)
+              Session_consistency_gtids_ctx::Ctx_change_listener* listener,
+              THD* thd)
 {
   DBUG_ASSERT(m_listener == NULL || m_listener == listener);
   if (m_listener == NULL)
@@ -145,6 +152,13 @@ Session_consistency_gtids_ctx::register_ctx_change_listener(
     m_listener= listener;
     m_sid_map= new Sid_map(NULL);
     m_gtid_set= new Gtid_set(m_sid_map);
+
+    /*
+     Caches the value at startup if needed. This is called during THD::init,
+     if the session_track_gtids value is set at startup time to anything 
+     different than OFF.
+     */
+    m_curr_session_track_gtids= thd->variables.session_track_gtids;
   }
 }
 
diff --git a/sql/rpl_context.h b/sql/rpl_context.h
index d16df2637b93..2159560231ad 100644
--- a/sql/rpl_context.h
+++ b/sql/rpl_context.h
@@ -75,6 +75,17 @@ class Session_consistency_gtids_ctx
   */
   Session_consistency_gtids_ctx::Ctx_change_listener* m_listener;
 
+  /**
+   Keeps track of the current session track gtids, so that we capture
+   according to what was set before. For instance, if the user does:
+   SET @@SESSION.SESSION_TRACK_GTIDS='ALL_GTIDS';
+   ...
+   SET @@SESSION.SESSION_TRACK_GTIDS='OWN_GTID';
+
+   The last statement should return a set of GTIDs.
+  */
+  ulong m_curr_session_track_gtids;
+  
 protected:
 
   /*
@@ -111,15 +122,19 @@ class Session_consistency_gtids_ctx
    Registers the listener. The pointer MUST not be NULL.
 
    @param listener a pointer to the listener to register.
+   @param thd THD context associated to this listener.
   */
-  void register_ctx_change_listener(Session_consistency_gtids_ctx::Ctx_change_listener* listener);
+  void register_ctx_change_listener(
+    Session_consistency_gtids_ctx::Ctx_change_listener* listener,
+    THD* thd);
 
   /**
    Unregisters the listener. The listener MUST have registered previously.
 
    @param listener a pointer to the listener to register.
   */
-  void unregister_ctx_change_listener(Session_consistency_gtids_ctx::Ctx_change_listener* listener);
+  void unregister_ctx_change_listener(
+    Session_consistency_gtids_ctx::Ctx_change_listener* listener);
 
   /**
     This member function MUST return a reference to the set of collected
diff --git a/sql/session_tracker.cc b/sql/session_tracker.cc
index c1cc55525495..cc8e5c526a2a 100644
--- a/sql/session_tracker.cc
+++ b/sql/session_tracker.cc
@@ -1157,7 +1157,7 @@ bool Session_gtids_tracker::update(THD *thd)
   if (m_enabled)
   {
     // register to listen to gtids context state changes
-    thd->rpl_thd_ctx.session_gtids_ctx().register_ctx_change_listener(this);
+    thd->rpl_thd_ctx.session_gtids_ctx().register_ctx_change_listener(this, thd);
 
     // instantiate the encoder if needed
     if (m_encoder == NULL)
@@ -1174,15 +1174,7 @@ bool Session_gtids_tracker::update(THD *thd)
       m_encoder= new Session_gtids_ctx_encoder_string();
     }
   }
-  else // break the bridge between tracker and collector
-  {
-    /* No need to listen to gtids context state changes */
-    thd->rpl_thd_ctx.session_gtids_ctx().unregister_ctx_change_listener(this);
-
-    // delete the encoder (just to free memory)
-    delete m_encoder; // if not tracking, delete the encoder
-    m_encoder= NULL;
-  }
+  // else /* break the bridge between tracker and collector */
   return false;
 }
 
@@ -1202,10 +1194,9 @@ bool Session_gtids_tracker::update(THD *thd)
 
 bool Session_gtids_tracker::store(THD *thd, String &buf)
 {
-  if (m_encoder->encode(thd, buf))
+  if (m_encoder && m_encoder->encode(thd, buf))
     return true;
-  if (!buf.is_empty())
-    reset();
+  reset();
   return false;
 }
 
@@ -1232,5 +1223,18 @@ void Session_gtids_tracker::mark_as_changed(LEX_CSTRING *tracked_item_name
 
 void Session_gtids_tracker::reset()
 {
+  /*
+   Delete the encoder and remove the listener if this had been previously
+   deactivated.
+   */
+  if (!m_enabled && m_encoder)
+  {
+    /* No need to listen to gtids context state changes */
+    current_thd->rpl_thd_ctx.session_gtids_ctx().unregister_ctx_change_listener(this);
+
+    // delete the encoder (just to free memory)
+    delete m_encoder; // if not tracking, delete the encoder
+    m_encoder= NULL;
+  }
   m_changed= false;
-}
\ No newline at end of file
+}