diff --git a/src/unlocker/proxy.cpp b/src/unlocker/proxy.cpp
index 06ac8c0..61d1f3c 100644
--- a/src/unlocker/proxy.cpp
+++ b/src/unlocker/proxy.cpp
@@ -331,7 +331,9 @@ void Proxy::handleClient(SOCKET clientSocket)
                         {
                             size_t le = clientStream.buffer.find("\r\n", idx);
                             if (le == std::string::npos) break;
-                            int cs = stoiSafe(clientStream.buffer.substr(idx, le - idx), 0, 16);
+                            int cs = stoiSafe(clientStream.buffer.substr(idx, le - idx), -1, 16);
+                            if (cs < 0) return;
+
                             if (idx + (le - idx) + 2 + cs + 2 > clientStream.buffer.size()) break;
                             if (cs > 0) fullBody.append(clientStream.buffer, le + 2, cs);
                             idx = le + 2 + cs + 2;
@@ -402,7 +404,9 @@ void Proxy::handleClient(SOCKET clientSocket)
                     {
                         size_t le = serverStream.buffer.find("\r\n", idx);
                         if (le == std::string::npos) break;
-                        int cs = stoiSafe(serverStream.buffer.substr(idx, le - idx), 0, 16);
+                        int cs = stoiSafe(serverStream.buffer.substr(idx, le - idx), -1, 16);
+                        if (cs < 0) return;
+
                         if (idx + (le - idx) + 2 + cs + 2 > serverStream.buffer.size()) break;
                         if (cs > 0) fullBody.append(serverStream.buffer, le + 2, cs);
                         idx = le + 2 + cs + 2;