diff --git a/td/mtproto/ProxySecret.cpp b/td/mtproto/ProxySecret.cpp
index 51fa957cd..7fc5eef71 100644
--- a/td/mtproto/ProxySecret.cpp
+++ b/td/mtproto/ProxySecret.cpp
@@ -26,7 +26,7 @@ Result<ProxySecret> ProxySecret::from_link(Slice encoded_secret) {
 Result<ProxySecret> ProxySecret::from_binary(Slice raw_unchecked_secret) {
   if (raw_unchecked_secret.size() == 16 ||
       (raw_unchecked_secret.size() == 17 && static_cast<unsigned char>(raw_unchecked_secret[0]) == 0xdd) ||
-      (raw_unchecked_secret.size() >= 17 && static_cast<unsigned char>(raw_unchecked_secret[0]) == 0xee)) {
+      (raw_unchecked_secret.size() >= 18 && static_cast<unsigned char>(raw_unchecked_secret[0]) == 0xee)) {
     return from_raw(raw_unchecked_secret);
   }
   if (raw_unchecked_secret.size() < 16) {