diff --git a/Data/expansions/classic/expansion.json b/Data/expansions/classic/expansion.json
index b8d3181e..606a9aaf 100644
--- a/Data/expansions/classic/expansion.json
+++ b/Data/expansions/classic/expansion.json
@@ -4,7 +4,7 @@
   "shortName": "Classic",
   "version": { "major": 1, "minor": 12, "patch": 1 },
   "build": 5875,
-  "protocolVersion": 8,
+  "protocolVersion": 3,
   "maxLevel": 60,
   "races": [1, 2, 3, 4, 5, 6, 7, 8],
   "classes": [1, 2, 3, 4, 5, 7, 8, 9, 11]
diff --git a/Data/expansions/tbc/expansion.json b/Data/expansions/tbc/expansion.json
index c3af88cf..025f9a9b 100644
--- a/Data/expansions/tbc/expansion.json
+++ b/Data/expansions/tbc/expansion.json
@@ -4,7 +4,7 @@
   "shortName": "TBC",
   "version": { "major": 2, "minor": 4, "patch": 3 },
   "build": 8606,
-  "protocolVersion": 8,
+  "protocolVersion": 5,
   "maxLevel": 70,
   "races": [1, 2, 3, 4, 5, 6, 7, 8, 10, 11],
   "classes": [1, 2, 3, 4, 5, 6, 7, 8, 9, 11]
diff --git a/Data/expansions/turtle/expansion.json b/Data/expansions/turtle/expansion.json
index b0b032a0..c14f95a4 100644
--- a/Data/expansions/turtle/expansion.json
+++ b/Data/expansions/turtle/expansion.json
@@ -4,7 +4,7 @@
   "shortName": "Turtle",
   "version": { "major": 1, "minor": 12, "patch": 1 },
   "build": 5875,
-  "protocolVersion": 8,
+  "protocolVersion": 3,
   "maxLevel": 60,
   "races": [1, 2, 3, 4, 5, 6, 7, 8],
   "classes": [1, 2, 3, 4, 5, 7, 8, 9, 11]
diff --git a/src/auth/auth_handler.cpp b/src/auth/auth_handler.cpp
index 5bed9777..b5b91c96 100644
--- a/src/auth/auth_handler.cpp
+++ b/src/auth/auth_handler.cpp
@@ -167,7 +167,18 @@ void AuthHandler::handleLogonChallengeResponse(network::Packet& packet) {
     }
 
     if (!response.isSuccess()) {
-        fail(std::string("LOGON_CHALLENGE failed: ") + getAuthResultString(response.result));
+        if (response.result == AuthResult::BUILD_INVALID || response.result == AuthResult::BUILD_UPDATE) {
+            std::ostringstream ss;
+            ss << "LOGON_CHALLENGE failed: version mismatch (client v"
+               << (int)clientInfo.majorVersion << "."
+               << (int)clientInfo.minorVersion << "."
+               << (int)clientInfo.patchVersion
+               << " build " << clientInfo.build
+               << ", auth protocol " << (int)clientInfo.protocolVersion << ")";
+            fail(ss.str());
+        } else {
+            fail(std::string("LOGON_CHALLENGE failed: ") + getAuthResultString(response.result));
+        }
         return;
     }
 
@@ -353,13 +364,22 @@ void AuthHandler::handlePacket(network::Packet& packet) {
                 LogonChallengeResponse response;
                 if (LogonChallengeResponseParser::parse(packet, response) && !response.isSuccess()) {
                     std::ostringstream ss;
-                    ss << "Server cancelled authentication";
+                    ss << "LOGON_CHALLENGE failed";
                     if (state == AuthState::PIN_REQUIRED) {
                         ss << " while waiting for 2FA/PIN code";
                     }
-                    ss << ": " << getAuthResultString(response.result)
-                       << " (code 0x" << std::hex << std::setw(2) << std::setfill('0')
-                       << static_cast<unsigned>(response.result) << std::dec << ")";
+                    if (response.result == AuthResult::BUILD_INVALID || response.result == AuthResult::BUILD_UPDATE) {
+                        ss << ": version mismatch (client v"
+                           << (int)clientInfo.majorVersion << "."
+                           << (int)clientInfo.minorVersion << "."
+                           << (int)clientInfo.patchVersion
+                           << " build " << clientInfo.build
+                           << ", auth protocol " << (int)clientInfo.protocolVersion << ")";
+                    } else {
+                        ss << ": " << getAuthResultString(response.result)
+                           << " (code 0x" << std::hex << std::setw(2) << std::setfill('0')
+                           << static_cast<unsigned>(response.result) << std::dec << ")";
+                    }
                     fail(ss.str());
                 } else {
                     LOG_WARNING("Unexpected LOGON_CHALLENGE response in state: ", (int)state);
diff --git a/src/auth/auth_opcodes.cpp b/src/auth/auth_opcodes.cpp
index 338805cf..13611522 100644
--- a/src/auth/auth_opcodes.cpp
+++ b/src/auth/auth_opcodes.cpp
@@ -18,11 +18,9 @@ const char* getAuthResultString(AuthResult result) {
         case AuthResult::OUT_OF_CREDIT: return "Account out of credit/time";
         case AuthResult::BUSY: return "Server is busy - try again later";
         case AuthResult::BUILD_INVALID:
-            return "Version mismatch - this client is WotLK 3.3.5a (build 12340). "
-                   "The server requires a different client version";
+            return "Version mismatch - the server requires a different client build/version";
         case AuthResult::BUILD_UPDATE:
-            return "Client update required - the server expects a different build version. "
-                   "This client only supports WotLK 3.3.5a (build 12340)";
+            return "Client update required - the server expects a different client build/version";
         case AuthResult::INVALID_SERVER: return "Invalid server";
         case AuthResult::ACCOUNT_SUSPENDED: return "This account has been suspended";
         case AuthResult::ACCESS_DENIED: return "Access denied";