diff --git a/src/ccaosdb.cpp b/src/ccaosdb.cpp
index d18099c6ba1ea64b9a0a1389acf72427b7068cda..8797474ab8e2b879ceb7ae780c639349452bf084 100644
--- a/src/ccaosdb.cpp
+++ b/src/ccaosdb.cpp
@@ -26,6 +26,7 @@
 #include "caosdb/status_code.h"
 #include "caosdb/logging.h"
 #include <cassert>
+#include <cstring>
 #include <exception>
 #include <iostream>
 #include <stdio.h>
@@ -337,7 +338,9 @@ ERROR_RETURN_CODE(
       transaction->wrapped_transaction);
     // Fill a string vector with the contents of the array of char arrays.
     std::vector<std::string> str_ids;
+    std::cout << "Filling vector with ids ..." << std::endl;
     for (const char **i = ids; *i; ++i) {
+      std::cout << *i << ", empty: " << (strcmp(*i, "") == 0) << std::endl;
       str_ids.push_back(std::string(*i));
     }
     return wrapped_transaction->RetrieveById(str_ids.begin(), str_ids.end());