diff --git a/src/output.cpp b/src/output.cpp
index e277f4f627..5c6f2b677e 100644
--- a/src/output.cpp
+++ b/src/output.cpp
@@ -577,6 +577,7 @@ void write_tallies()
     return;
 
   // Set filename for tallies_out
+  std::string filename;
   filename = fmt::format("{}tallies.out", settings::path_output);
 
   // Open the tallies.out file.
diff --git a/src/summary.cpp b/src/summary.cpp
index 3075f621f6..1915fde334 100644
--- a/src/summary.cpp
+++ b/src/summary.cpp
@@ -23,6 +23,7 @@ void write_summary()
   write_message("Writing summary.h5 file...", 5);
 
   // Set filename for summary file
+  std::string filename;
   filename = fmt::format("{}summary.h5", settings::path_output);
 
   // Create a new file using default properties.