diff --git a/quic/core/crypto/crypto_protocol.h b/quic/core/crypto/crypto_protocol.h
index e45d73a..52afa9c 100644
--- a/quic/core/crypto/crypto_protocol.h
+++ b/quic/core/crypto/crypto_protocol.h
@@ -29,7 +29,7 @@
 // The following tags have been deprecated and should not be reused:
 // "1CON", "BBQ4", "NCON", "RCID", "SREJ", "TBKP", "TB10", "SCLS", "SMHL",
 // "QNZR", "B2HI", "H2PR", "FIFO", "LIFO", "RRWS", "QNSP", "B2CL", "CHSP",
-// "BPTE"
+// "BPTE", "ACKD"
 
 // clang-format off
 const QuicTag kCHLO = TAG('C', 'H', 'L', 'O');   // Client hello
@@ -170,7 +170,6 @@
 const QuicTag kMAD5 = TAG('M', 'A', 'D', '5');   // IETF style TLP with 2x mult
 const QuicTag k1ACK = TAG('1', 'A', 'C', 'K');   // 1 fast ack for reordering
 const QuicTag kACD0 = TAG('A', 'D', 'D', '0');   // Disable ack decimation
-const QuicTag kACKD = TAG('A', 'C', 'K', 'D');   // Ack decimation style acking.
 const QuicTag kAKD2 = TAG('A', 'K', 'D', '2');   // Ack decimation tolerating
                                                  // out of order packets.
 const QuicTag kAKD3 = TAG('A', 'K', 'D', '3');   // Ack decimation style acking
diff --git a/quic/core/quic_connection_test.cc b/quic/core/quic_connection_test.cc
index 68ee43b..a3b9f90 100644
--- a/quic/core/quic_connection_test.cc
+++ b/quic/core/quic_connection_test.cc
@@ -6553,7 +6553,6 @@
   EXPECT_CALL(*send_algorithm_, SetFromConfig(_, _));
   QuicConfig config;
   QuicTagVector connection_options;
-  connection_options.push_back(kACKD);
   // No limit on the number of packets received before sending an ack.
   connection_options.push_back(kAKDU);
   config.SetConnectionOptionsToSend(connection_options);
diff --git a/quic/core/quic_received_packet_manager_test.cc b/quic/core/quic_received_packet_manager_test.cc
index da586c6..9d6b664 100644
--- a/quic/core/quic_received_packet_manager_test.cc
+++ b/quic/core/quic_received_packet_manager_test.cc
@@ -434,7 +434,6 @@
   EXPECT_FALSE(HasPendingAck());
   QuicConfig config;
   QuicTagVector connection_options;
-  connection_options.push_back(kACKD);
   // No limit on the number of packets received before sending an ack.
   connection_options.push_back(kAKDU);
   config.SetConnectionOptionsToSend(connection_options);
diff --git a/quic/core/uber_received_packet_manager_test.cc b/quic/core/uber_received_packet_manager_test.cc
index cf612fe..77731fb 100644
--- a/quic/core/uber_received_packet_manager_test.cc
+++ b/quic/core/uber_received_packet_manager_test.cc
@@ -368,7 +368,6 @@
   EXPECT_FALSE(HasPendingAck());
   QuicConfig config;
   QuicTagVector connection_options;
-  connection_options.push_back(kACKD);
   // No limit on the number of packets received before sending an ack.
   connection_options.push_back(kAKDU);
   config.SetConnectionOptionsToSend(connection_options);