diff --git a/src/server/authserver/Server/AuthSession.cpp b/src/server/authserver/Server/AuthSession.cpp
index 37bbade765d..3fb34ac478f 100644
--- a/src/server/authserver/Server/AuthSession.cpp
+++ b/src/server/authserver/Server/AuthSession.cpp
@@ -479,7 +479,7 @@ bool AuthSession::HandleLogonProof()
     A.SetBinary(logonProof->A, 32);
 
     // SRP safeguard: abort if A == 0
-    if (A.IsZero())
+    if ((A % N).IsZero())
         return false;
 
     SHA1Hash sha;