diff --git a/src/nuclide.cpp b/src/nuclide.cpp
index 59e5f6e8c0..0a0e400578 100644
--- a/src/nuclide.cpp
+++ b/src/nuclide.cpp
@@ -944,7 +944,7 @@ extern "C" int openmc_load_nuclide(const char* name, const double* temps, int n)
     // Get filename for library containing nuclide
     int idx = it->second;
     const auto& filename = data::libraries[idx].path_;
-    write_message("Reading " + std::string{name} + " from " + filename, 6);
+    write_message(6, "Reading {} from {}", std::string{name}, filename);
 
     // Open file and make sure version is sufficient
     hid_t file_id = file_open(filename, 'r');
@@ -977,7 +977,7 @@ extern "C" int openmc_load_nuclide(const char* name, const double* temps, int n)
 
         int idx = it->second;
         const auto& filename = data::libraries[idx].path_;
-        write_message("Reading " + element + " from " + filename, 6);
+        write_message(6, "Reading {} from {} ", element, filename);
 
         // Open file and make sure version is sufficient
         hid_t file_id = file_open(filename, 'r');