diff --git a/FPEngine.cc b/FPEngine.cc
index 7155db923..98aa44b41 100644
--- a/FPEngine.cc
+++ b/FPEngine.cc
@@ -1495,8 +1495,8 @@ int FPHost::update_RTO(int measured_rtt_usecs, bool retransmission) {
   *
   *  RTO <- SRTT + max (G, K*RTTVAR)
   */
-    this->rttvar = ((1.0 - 0.25) * this->rttvar) + (0.25 * ABS(this->srtt - measured_rtt_usecs));
-    this->srtt = ((1.0 - 0.125) * this->srtt) + (0.125 * measured_rtt_usecs);
+    this->rttvar += (ABS(this->srtt - measured_rtt_usecs) - this->rttvar) >> 2;
+    this->srtt += (measured_rtt_usecs - this->srtt) >> 3;
     this->rto = this->srtt + MAX(500000, 4*this->rttvar);
   }