diff --git a/vowpalwabbit/core/src/vw_validate.cc b/vowpalwabbit/core/src/vw_validate.cc
index f46db2e076e..8759ed9f46d 100644
--- a/vowpalwabbit/core/src/vw_validate.cc
+++ b/vowpalwabbit/core/src/vw_validate.cc
@@ -38,11 +38,11 @@ void validate_num_bits(VW::workspace& all)
   {
     if (all.weights.sparse)
     {
-      std::stringstream ss;
-      ss << "Bit size is " << all.initial_weights_config.num_bits
-         << ". While this is allowed for sparse weights, it may cause an overflow and is strongly recommened to use a "
-            "smaller value.";
-      all.logger.err_warn(ss.str());
+      std::string warning = fmt::format(
+          "Bit size is {}. While this is allowed for sparse weights, it may cause an overflow and is strongly "
+          "recommended to use a smaller value.",
+          all.initial_weights_config.num_bits);
+      all.logger.err_warn(warning);
     }
     else
     {