diff --git a/pdns/auth-catalogzone.cc b/pdns/auth-catalogzone.cc
index 2fd7369283fe..bcff734f082d 100644
--- a/pdns/auth-catalogzone.cc
+++ b/pdns/auth-catalogzone.cc
@@ -107,7 +107,7 @@ std::string CatalogInfo::toJson() const
 
 void CatalogInfo::updateHash(CatalogHashMap& hashes, const DomainInfo& di) const
 {
-  hashes[di.catalog].process(std::to_string(di.id) + di.zone.toLogString() + "\0" + d_coo.toLogString() + "\0" + d_unique.toLogString());
+  hashes[di.catalog].process(std::to_string(di.id) + di.zone.toLogString() + string("\0", 1) + d_coo.toLogString() + string("\0", 1) + d_unique.toLogString());
   for (const auto& group : d_group) {
     hashes[di.catalog].process(std::to_string(group.length()) + group);
   }