diff --git a/library/bignum_mod_raw.c b/library/bignum_mod_raw.c
index 2f49ea2d9e..22e56b7e63 100644
--- a/library/bignum_mod_raw.c
+++ b/library/bignum_mod_raw.c
@@ -52,11 +52,12 @@ void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
 int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
                               const mbedtls_mpi_mod_modulus *m,
                               const unsigned char *input,
-                              size_t input_length )
+                              size_t input_length,
+                              mbedtls_mpi_mod_ext_rep ext_rep )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
-    switch( m->ext_rep )
+    switch( ext_rep )
     {
         case MBEDTLS_MPI_MOD_EXT_REP_LE:
             ret = mbedtls_mpi_core_read_le( X, m->limbs,
@@ -87,9 +88,10 @@ cleanup:
 int mbedtls_mpi_mod_raw_write( const mbedtls_mpi_uint *A,
                                const mbedtls_mpi_mod_modulus *m,
                                unsigned char *output,
-                               size_t output_length )
+                               size_t output_length,
+                               mbedtls_mpi_mod_ext_rep ext_rep )
 {
-    switch( m->ext_rep )
+    switch( ext_rep )
     {
         case MBEDTLS_MPI_MOD_EXT_REP_LE:
             return( mbedtls_mpi_core_write_le( A, m->limbs,
diff --git a/library/bignum_mod_raw.h b/library/bignum_mod_raw.h
index f6c6ebd8f2..d7b6dd115e 100644
--- a/library/bignum_mod_raw.h
+++ b/library/bignum_mod_raw.h
@@ -106,6 +106,7 @@ void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
  * \param[in] m         The address of the modulus related to \p X.
  * \param[in] input     The input buffer to import from.
  * \param input_length  The length in bytes of \p input.
+ * \param ext_rep       The endianness of the number in the input buffer.
  *
  * \return       \c 0 if successful.
  * \return       #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
@@ -116,7 +117,8 @@ void mbedtls_mpi_mod_raw_cond_swap( mbedtls_mpi_uint *X,
 int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
                               const mbedtls_mpi_mod_modulus *m,
                               const unsigned char *input,
-                              size_t input_length );
+                              size_t input_length,
+                              mbedtls_mpi_mod_ext_rep ext_rep );
 
 /** Export A into unsigned binary data.
  *
@@ -126,6 +128,7 @@ int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
  * \param[in] m         The address of the modulus related to \p A.
  * \param[out] output   The output buffer to export to.
  * \param output_length The length in bytes of \p output.
+ * \param ext_rep       The endianness in which the number should be written into the output buffer.
  *
  * \return       \c 0 if successful.
  * \return       #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p output isn't
@@ -136,7 +139,8 @@ int mbedtls_mpi_mod_raw_read( mbedtls_mpi_uint *X,
 int mbedtls_mpi_mod_raw_write( const mbedtls_mpi_uint *A,
                                const mbedtls_mpi_mod_modulus *m,
                                unsigned char *output,
-                               size_t output_length );
+                               size_t output_length,
+                               mbedtls_mpi_mod_ext_rep ext_rep );
 
 /* BEGIN MERGE SLOT 1 */
 
diff --git a/tests/suites/test_suite_bignum_mod_raw.function b/tests/suites/test_suite_bignum_mod_raw.function
index 00ed005f50..031897889c 100644
--- a/tests/suites/test_suite_bignum_mod_raw.function
+++ b/tests/suites/test_suite_bignum_mod_raw.function
@@ -54,17 +54,17 @@ void mpi_mod_raw_io( data_t *input, int nb_int, int nx_32_int,
     TEST_EQUAL( ret, 0 );
 
     if( iendian == MBEDTLS_MPI_MOD_EXT_REP_INVALID && iret != 0 )
-        m.ext_rep = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
+       endian = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
 
-    ret = mbedtls_mpi_mod_raw_read( X, &m, input->x, input->len );
+    ret = mbedtls_mpi_mod_raw_read( X, &m, input->x, input->len, endian );
     TEST_EQUAL( ret, iret );
 
     if( iret == 0 )
     {
         if( iendian == MBEDTLS_MPI_MOD_EXT_REP_INVALID && oret != 0 )
-            m.ext_rep = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
+            endian = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
 
-        ret = mbedtls_mpi_mod_raw_write( X, &m, buf, nb );
+        ret = mbedtls_mpi_mod_raw_write( X, &m, buf, nb, endian );
         TEST_EQUAL( ret, oret );
     }