diff --git a/folly/IPAddressV4.cpp b/folly/IPAddressV4.cpp
index fb6c19d7bd9..d5ca25a28da 100644
--- a/folly/IPAddressV4.cpp
+++ b/folly/IPAddressV4.cpp
@@ -232,6 +232,7 @@ bool IPAddressV4::isPrivate() const {
       (ip >= 0xA9FE0000 && ip <= 0xA9FEFFFF) || // 169.254.0.0-169.254.255.255
       (ip >= 0xAC100000 && ip <= 0xAC1FFFFF) || // 172.16.0.0-172.31.255.255
       (ip >= 0xC0A80000 && ip <= 0xC0A8FFFF) || // 192.168.0.0-192.168.255.255
+      (ip >= 0x64400000 && ip <= 0x647fffff) || // 100.64.0.0-100.127.255.255
       false;
 }