diff --git a/quic/core/quic_constants.h b/quic/core/quic_constants.h
index eaf0170..a1126c0 100644
--- a/quic/core/quic_constants.h
+++ b/quic/core/quic_constants.h
@@ -265,6 +265,8 @@
 // This intends to avoid the beginning of slow start, when CWNDs may be
 // rapidly increasing.
 const QuicPacketCount kMinReceivedBeforeAckDecimation = 100;
+// One quarter RTT delay when doing ack decimation.
+const float kAckDecimationDelay = 0.25;
 
 // The default alarm granularity assumed by QUIC code.
 const QuicTime::Delta kAlarmGranularity = QuicTime::Delta::FromMilliseconds(1);
diff --git a/quic/core/quic_received_packet_manager.cc b/quic/core/quic_received_packet_manager.cc
index 9a84d97..0a91709 100644
--- a/quic/core/quic_received_packet_manager.cc
+++ b/quic/core/quic_received_packet_manager.cc
@@ -26,8 +26,6 @@
 // against an ack loss
 const size_t kMaxPacketsAfterNewMissing = 4;
 
-// One quarter RTT delay when doing ack decimation.
-const float kAckDecimationDelay = 0.25;
 // One eighth RTT delay when doing ack decimation.
 const float kShortAckDecimationDelay = 0.125;
 }  // namespace
diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index 106393b..b98f65c 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -59,11 +59,6 @@
 // losses.
 static const uint32_t kConservativeUnpacedBurst = 2;
 
-// TODO(haoyuewang) Unify this constant and kAckDecimationDelay in
-// quic_received_packet_manager.cc.
-// Ack delay as (RTT >> kAckDelayShift).
-static const int kAckDelayShift = 2;
-
 }  // namespace
 
 #define ENDPOINT                                                         \
@@ -731,7 +726,7 @@
   QUIC_RELOADABLE_FLAG_COUNT(quic_can_send_ack_frequency);
   frame.packet_tolerance = kMaxRetransmittablePacketsBeforeAck;
   auto rtt = rtt_stats_.MinOrInitialRtt();
-  frame.max_ack_delay = rtt >> kAckDelayShift;
+  frame.max_ack_delay = rtt * kAckDecimationDelay;
   frame.max_ack_delay = std::max(frame.max_ack_delay, peer_min_ack_delay_);
 
   return frame;