From bf8ba52f27af3e2293d99f9999f453d21380556a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franz=20P=C3=B6schel?= <franz.poeschel@gmail.com>
Date: Mon, 20 Apr 2026 18:22:23 +0200
Subject: [PATCH] Do not initially emplace any value for the cached Iteration
 index

this avoids subtle bugs
followup to #1860
---
 include/openPMD/Iteration.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/openPMD/Iteration.hpp b/include/openPMD/Iteration.hpp
index e2a4e6b1a5..abce61eef7 100644
--- a/include/openPMD/Iteration.hpp
+++ b/include/openPMD/Iteration.hpp
@@ -136,7 +136,7 @@ namespace internal
          * of the owning map entry instead of a linear scan in
          * <code>Series::indexOf()</code>.
          */
-        std::optional<uint64_t> m_iterationIndex = 0;
+        std::optional<uint64_t> m_iterationIndex = std::nullopt;
 
         /**
          * Information on a parsing request that has not yet been executed.