diff --git a/cpp/include/kvikio/shim/libcurl.hpp b/cpp/include/kvikio/shim/libcurl.hpp
index 635ea4c7fd..39c3e89320 100644
--- a/cpp/include/kvikio/shim/libcurl.hpp
+++ b/cpp/include/kvikio/shim/libcurl.hpp
@@ -163,8 +163,14 @@ class CurlHandle {
       _source_line(std::move(source_line))
   {
     // Removing all '\0' characters
+    auto _source_file_size = _source_file.size();
     _source_file.erase(std::remove(_source_file.begin(), _source_file.end(), '\0'),
                        _source_file.end());
+    if(_source_file_size != _source_file.size()) {
+      std::stringstream ss;
+      ss << "CurlHandle - `source_file` contains " << _source_file_size - _source_file.size() << " '\\0' chars?!?";
+      throw std::runtime_error(ss.str());
+    }
 
     // Need CURLOPT_NOSIGNAL to support threading, see
     // <https://curl.se/libcurl/c/CURLOPT_NOSIGNAL.html>