diff --git a/library/bignum_mod.h b/library/bignum_mod.h
index 7eac1df1cc..432cd00708 100644
--- a/library/bignum_mod.h
+++ b/library/bignum_mod.h
@@ -56,8 +56,12 @@ typedef enum
     MBEDTLS_MPI_MOD_REP_OPT_RED
 } mbedtls_mpi_mod_rep_selector;
 
-#define MBEDTLS_MPI_MOD_EXT_REP_LE   0x1
-#define MBEDTLS_MPI_MOD_EXT_REP_BE   0x2
+typedef enum
+{
+    MBEDTLS_MPI_MOD_EXT_REP_INVALID    = 0,
+    MBEDTLS_MPI_MOD_EXT_REP_LE,
+    MBEDTLS_MPI_MOD_EXT_REP_BE
+} mbedtls_mpi_mod_ext_rep;
 
 void mbedtls_mpi_mod_residue_release( mbedtls_mpi_mod_residue *r );
 
diff --git a/library/bignum_new.c b/library/bignum_new.c
index b6a806ecbc..5f10eadcd1 100644
--- a/library/bignum_new.c
+++ b/library/bignum_new.c
@@ -114,7 +114,11 @@ void mbedtls_mpi_mod_modulus_init( mbedtls_mpi_mod_modulus *m )
     if ( m == NULL )
         return;
 
-    m->rep.mont = 0;
+    m->p = NULL;
+    m->n = 0;
+    m->plen = 0;
+    m->ext_rep = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
+    m->int_rep = MBEDTLS_MPI_MOD_REP_INVALID;
 }
 
 void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m )
@@ -125,10 +129,8 @@ void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m )
     m->p = NULL;
     m->n = 0;
     m->plen = 0;
-    m->ext_rep = 0;
-    m->int_rep = 0;
-    m->rep.mont = NULL;
-    m->rep.ored = NULL;
+    m->ext_rep = MBEDTLS_MPI_MOD_EXT_REP_INVALID;
+    m->int_rep = MBEDTLS_MPI_MOD_REP_INVALID;
 }
 
 int mbedtls_mpi_mod_modulus_setup( mbedtls_mpi_mod_modulus *m,