diff --git a/src/ROOTNTupleWriter.cc b/src/ROOTNTupleWriter.cc
index dfa75badf..9cf3b9d8d 100644
--- a/src/ROOTNTupleWriter.cc
+++ b/src/ROOTNTupleWriter.cc
@@ -71,7 +71,7 @@ void ROOTNTupleWriter::writeFrame(const podio::Frame& frame, const std::string&
   const bool new_category = (catInfo.writer == nullptr);
   if (new_category) {
     // This is the minimal information that we need for now
-    catInfo.name = collsToWrite;
+    catInfo.name = root_utils::sortAlphabeticaly(collsToWrite);
   }
 
   std::vector<StoreCollection> collections;
diff --git a/src/rootUtils.h b/src/rootUtils.h
index 648a6f166..acc552f24 100644
--- a/src/rootUtils.h
+++ b/src/rootUtils.h
@@ -287,9 +287,16 @@ inline bool checkConsistentColls(const std::vector<std::string>& existingColls,
 
   // Since we are guaranteed to have unique names here, we can just look for
   // collisions brute force, which seems to be quickest approach for vector
-  // sizes we typically have here (few hundred)
+  // sizes we typically have (few hundred). We can take advantage of the fact
+  // that the existingColls are ordered (alphabetically and case-insensitive),
+  // so we can do a binary_search
   for (const auto& id : candidateColls) {
-    if (std::find(existingColls.begin(), existingColls.end(), id) == existingColls.end()) {
+    if (!std::binary_search(existingColls.begin(), existingColls.end(), id, [](const auto& lhs, const auto& rhs) {
+          return lhs.size() == rhs.size() &&
+              std::lexicographical_compare(
+                     lhs.begin(), lhs.end(), rhs.begin(), rhs.end(),
+                     [](const auto cl, const auto cr) { return std::tolower(cl) < std::tolower(cr); });
+        })) {
       return false;
     }
   }