diff --git a/src/Benchmarks/BLAS/tnl-benchmark-blas.h b/src/Benchmarks/BLAS/tnl-benchmark-blas.h
index 6419087a93b393fe1ee0d4ad56c5bbba6252ce56..8c78205e76df75f7541e9cc3c6098f5199c19b3c 100644
--- a/src/Benchmarks/BLAS/tnl-benchmark-blas.h
+++ b/src/Benchmarks/BLAS/tnl-benchmark-blas.h
@@ -43,7 +43,7 @@ runBlasBenchmarks( Benchmark & benchmark,
                            metadata );
    for( std::size_t size = minSize; size <= maxSize; size *= 2 ) {
       benchmark.setMetadataColumns( Benchmark::MetadataColumns({
-         {"size", String( size ) },
+         {"size", convertToString( size ) },
       } ));
       benchmarkArrayOperations< Real >( benchmark, loops, size );
    }
@@ -53,7 +53,7 @@ runBlasBenchmarks( Benchmark & benchmark,
                            metadata );
    for( std::size_t size = minSize; size <= maxSize; size *= sizeStepFactor ) {
       benchmark.setMetadataColumns( Benchmark::MetadataColumns({
-         { "size", String( size ) },
+         { "size", convertToString( size ) },
       } ));
       benchmarkVectorOperations< Real >( benchmark, loops, size );
    }
@@ -63,9 +63,9 @@ runBlasBenchmarks( Benchmark & benchmark,
                            metadata );
    for( std::size_t size = minSize; size <= maxSize; size *= 2 ) {
       benchmark.setMetadataColumns( Benchmark::MetadataColumns({
-         {"rows", String( size ) },
-         {"columns", String( size ) },
-         {"elements per row", String( elementsPerRow ) },
+         {"rows", convertToString( size ) },
+         {"columns", convertToString( size ) },
+         {"elements per row", convertToString( elementsPerRow ) },
       } ));
       benchmarkSpmvSynthetic< Real >( benchmark, loops, size, elementsPerRow );
    }