diff --git a/include/openPMD/backend/Writable.hpp b/include/openPMD/backend/Writable.hpp
index 25a2154665..1774d9dd59 100644
--- a/include/openPMD/backend/Writable.hpp
+++ b/include/openPMD/backend/Writable.hpp
@@ -121,7 +121,7 @@ class Writable final
      * it.
      */
     template <bool flush_entire_series>
-    void seriesFlush(std::string backendConfig = "{}");
+    void seriesFlush(std::string const &backendConfig = "{}");
 
     // clang-format off
 OPENPMD_private
diff --git a/src/backend/Writable.cpp b/src/backend/Writable.cpp
index fe9961fd96..47fcfd7933 100644
--- a/src/backend/Writable.cpp
+++ b/src/backend/Writable.cpp
@@ -46,13 +46,12 @@ Writable::~Writable()
 }
 
 template <bool flush_entire_series>
-void Writable::seriesFlush(std::string backendConfig)
+void Writable::seriesFlush(std::string const &backendConfig)
 {
-    seriesFlush<flush_entire_series>(
-        {FlushLevel::UserFlush, std::move(backendConfig)});
+    seriesFlush<flush_entire_series>({FlushLevel::UserFlush, backendConfig});
 }
-template void Writable::seriesFlush<true>(std::string backendConfig);
-template void Writable::seriesFlush<false>(std::string backendConfig);
+template void Writable::seriesFlush<true>(std::string const &backendConfig);
+template void Writable::seriesFlush<false>(std::string const &backendConfig);
 
 template <bool flush_entire_series>
 void Writable::seriesFlush(internal::FlushParams const &flushParams)