diff --git a/quic/QuicConstants.h b/quic/QuicConstants.h
index 374faa788..1f77a22a8 100644
--- a/quic/QuicConstants.h
+++ b/quic/QuicConstants.h
@@ -341,6 +341,7 @@ enum class QuicVersion : uint32_t {
   MVFST = 0xfaceb002,
   QUIC_V1 = 0x00000001,
   QUIC_V1_ALIAS = 0xfaceb003,
+  // MVFST_EXPERIMENTAL used to set initial congestion window
   MVFST_EXPERIMENTAL = 0xfaceb00e, // Experimental alias for MVFST
   MVFST_ALIAS = 0xfaceb010,
   MVFST_INVALID = 0xfaceb00f,
diff --git a/quic/server/QuicServerWorker.cpp b/quic/server/QuicServerWorker.cpp
index 58194b586..2e2e5fe56 100644
--- a/quic/server/QuicServerWorker.cpp
+++ b/quic/server/QuicServerWorker.cpp
@@ -650,6 +650,9 @@ QuicServerTransport::Ptr QuicServerWorker::makeTransport(
     }
     trans->setCongestionControllerFactory(ccFactory_);
     trans->setTransportStatsCallback(statsCallback_.get()); // ok if nullptr
+    if (quicVersion == QuicVersion::MVFST_EXPERIMENTAL) {
+      transportSettings_.initCwndInMss = 35;
+    }
 
     auto transportSettings = transportSettingsOverrideFn_
         ? transportSettingsOverrideFn_(
diff --git a/quic/server/state/ServerStateMachine.cpp b/quic/server/state/ServerStateMachine.cpp
index 169bb5ed5..d7f08f4d0 100644
--- a/quic/server/state/ServerStateMachine.cpp
+++ b/quic/server/state/ServerStateMachine.cpp
@@ -93,6 +93,8 @@ void recoverOrResetCongestionAndRttState(
 void maybeSetExperimentalSettings(QuicServerConnectionState& conn) {
   // no-op versions
   if (conn.version == QuicVersion::MVFST_EXPERIMENTAL) {
+    // MVFST_EXPERIMENTAL is used to set initCwnd
+    // QuicServerWorker.cpp before CC is initialized.
   } else if (conn.version == QuicVersion::MVFST_EXPERIMENTAL2) {
   } else if (conn.version == QuicVersion::MVFST_EXPERIMENTAL3) {
   }