diff --git a/nalgebra-sparse/src/io/matrix_market.rs b/nalgebra-sparse/src/io/matrix_market.rs
index 8acedd77..c644c34f 100644
--- a/nalgebra-sparse/src/io/matrix_market.rs
+++ b/nalgebra-sparse/src/io/matrix_market.rs
@@ -508,9 +508,9 @@ mod internal {
         /// When matrix is a Hermitian matrix, it will convert itself to its conjugate.
         fn conjugate(self) -> Result<Self, MatrixMarketError>;
         /// Returns the name of SupportedMatrixMarketScalar, used when write the matrix
-        fn typename() -> &'static [u8];
-        /// Convert the data to bytes
-        fn to_matrixmarket_bytes(&self) -> Vec<u8>;
+        fn typename() -> &'static str;
+        /// Write the data self to w
+        fn write_matrix_market<W: std::fmt::Write>(&self, w: W) -> Result<(), std::fmt::Error>;
     }
 
     pub trait SupportedMatrixMarketExport<T: SupportedMatrixMarketScalar> {
@@ -574,12 +574,15 @@ macro_rules! mm_int_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static [u8] {
-                b"integer"
+            fn typename() -> &'static str {
+                "integer"
             }
             #[inline]
-            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                self.to_string().into_bytes()
+            fn write_matrix_market<W: std::fmt::Write>(
+                &self,
+                mut w: W,
+            ) -> Result<(), std::fmt::Error> {
+                write!(w, "{}", self)
             }
         }
     };
@@ -627,12 +630,15 @@ macro_rules! mm_real_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static [u8] {
-                b"real"
+            fn typename() -> &'static str {
+                "real"
             }
             #[inline]
-            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                self.to_string().into_bytes()
+            fn write_matrix_market<W: std::fmt::Write>(
+                &self,
+                mut w: W,
+            ) -> Result<(), std::fmt::Error> {
+                write!(w, "{}", self)
             }
         }
     };
@@ -681,12 +687,15 @@ macro_rules! mm_complex_impl {
                 Ok(-self)
             }
             #[inline]
-            fn typename() -> &'static [u8] {
-                b"complex"
+            fn typename() -> &'static str {
+                "complex"
             }
             #[inline]
-            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                (self.re.to_string() + " " + &self.im.to_string()).into_bytes()
+            fn write_matrix_market<W: std::fmt::Write>(
+                &self,
+                mut w: W,
+            ) -> Result<(), std::fmt::Error> {
+                write!(w, "{} {}", self.re, self.im)
             }
         }
     };
@@ -738,12 +747,15 @@ macro_rules! mm_pattern_impl {
                 ))
             }
             #[inline]
-            fn typename() -> &'static [u8] {
-                b"pattern"
+            fn typename() -> &'static str {
+                "pattern"
             }
             #[inline]
-            fn to_matrixmarket_bytes(&self) -> Vec<u8> {
-                Vec::<u8>::new()
+            fn write_matrix_market<W: std::fmt::Write>(
+                &self,
+                mut _w: W,
+            ) -> Result<(), std::fmt::Error> {
+                Ok(())
             }
         }
     };
@@ -1448,9 +1460,9 @@ pub fn write_to_matrix_market_str<T: MatrixMarketScalar, S: MatrixMarketExport<T
     // The vector will grow as needed.
     // So, unwrap here won't cause any issue.
     write_to_matrix_market(&mut bytes, sparse_matrix).unwrap();
-    // safety issue is because 'from_utf8_unchecked' does not check that the bytes passed to it are valid UTF-8.
-    // Since 'bytes' created here is valid UTF-8 data, so it will not cause any problem.
-    unsafe { String::from_utf8_unchecked(bytes) }
+
+    String::from_utf8(bytes)
+        .expect("Unexpected non UTF-8 data was generated when export to matrix market string")
 }
 
 /// Write a sparse matrix into Matrix Market format file.
@@ -1486,7 +1498,7 @@ pub fn write_to_matrix_market_file<
 >(
     sparse_matrix: &S,
     path: P,
-) -> Result<(), MatrixMarketError> {
+) -> Result<(), std::io::Error> {
     let mut file = File::create(path)?;
     write_to_matrix_market(&mut file, sparse_matrix)?;
     Ok(())
@@ -1494,33 +1506,35 @@ pub fn write_to_matrix_market_file<
 
 /// low level implementation of writing sparse matrix into any [std::io::Write] object
 fn write_to_matrix_market<T: MatrixMarketScalar, S: MatrixMarketExport<T>, W: Write>(
-    w: &mut W,
+    mut w: W,
     sparse_matrix: &S,
-) -> Result<(), MatrixMarketError> {
+) -> Result<(), std::io::Error> {
     // write header
-    w.write_all(b"%%matrixmarket matrix coordinate ")?;
-    w.write_all(T::typename())?;
-    w.write_all(b" general\n")?;
+    writeln!(
+        w,
+        "%%matrixmarket matrix coordinate {} general",
+        T::typename()
+    )?;
 
     //write comment
-    w.write_all(b"% matrixmarket file generated by nalgebra-sparse.\n")?;
+    writeln!(w, "% matrixmarket file generated by nalgebra-sparse.")?;
 
     // write shape information
-    w.write_all(sparse_matrix.nrows().to_string().as_bytes())?;
-    w.write_all(b" ")?;
-    w.write_all(sparse_matrix.ncols().to_string().as_bytes())?;
-    w.write_all(b" ")?;
-    w.write_all(sparse_matrix.nnz().to_string().as_bytes())?;
-    w.write_all(b"\n")?;
+    writeln!(
+        w,
+        "{} {} {}",
+        sparse_matrix.nrows(),
+        sparse_matrix.ncols(),
+        sparse_matrix.nnz()
+    )?;
 
     //write triplets
+    let mut buffer = String::new();
     for (r, c, d) in sparse_matrix.triplet_iter() {
-        w.write_all((r + 1).to_string().as_bytes())?;
-        w.write_all(b"  ")?;
-        w.write_all((c + 1).to_string().as_bytes())?;
-        w.write_all(b"  ")?;
-        w.write_all(&d.to_matrixmarket_bytes())?;
-        w.write_all(b"\n")?;
+        buffer.clear();
+        d.write_matrix_market(&mut buffer)
+            .expect("Unexpected format error was generated when write to String");
+        writeln!(w, "{} {} {} ", r + 1, c + 1, buffer)?;
     }
     Ok(())
 }