diff --git a/library/pk_wrap.c b/library/pk_wrap.c
index db6274c..bdc0f39 100644
--- a/library/pk_wrap.c
+++ b/library/pk_wrap.c
@@ -68,7 +68,8 @@
 
 static size_t rsa_get_bitlen( const void *ctx )
 {
-    return( 8 * ((const mbedtls_rsa_context *) ctx)->len );
+    const mbedtls_rsa_context * rsa = (const mbedtls_rsa_context *) ctx;
+    return( 8 * mbedtls_rsa_get_len( rsa ) );
 }
 
 static int rsa_verify_wrap( void *ctx, mbedtls_md_type_t md_alg,
@@ -76,21 +77,23 @@
                    const unsigned char *sig, size_t sig_len )
 {
     int ret;
+    mbedtls_rsa_context * rsa = (mbedtls_rsa_context *) ctx;
+    size_t rsa_len = mbedtls_rsa_get_len( rsa );
 
 #if defined(MBEDTLS_HAVE_INT64)
     if( md_alg == MBEDTLS_MD_NONE && UINT_MAX < hash_len )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 #endif /* MBEDTLS_HAVE_INT64 */
 
-    if( sig_len < ((mbedtls_rsa_context *) ctx)->len )
+    if( sig_len < rsa_len )
         return( MBEDTLS_ERR_RSA_VERIFY_FAILED );
 
-    if( ( ret = mbedtls_rsa_pkcs1_verify( (mbedtls_rsa_context *) ctx, NULL, NULL,
+    if( ( ret = mbedtls_rsa_pkcs1_verify( rsa, NULL, NULL,
                                   MBEDTLS_RSA_PUBLIC, md_alg,
                                   (unsigned int) hash_len, hash, sig ) ) != 0 )
         return( ret );
 
-    if( sig_len > ((mbedtls_rsa_context *) ctx)->len )
+    if( sig_len > rsa_len )
         return( MBEDTLS_ERR_PK_SIG_LEN_MISMATCH );
 
     return( 0 );
@@ -101,14 +104,16 @@
                    unsigned char *sig, size_t *sig_len,
                    int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
+    mbedtls_rsa_context * rsa = (mbedtls_rsa_context *) ctx;
+
 #if defined(MBEDTLS_HAVE_INT64)
     if( md_alg == MBEDTLS_MD_NONE && UINT_MAX < hash_len )
         return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
 #endif /* MBEDTLS_HAVE_INT64 */
 
-    *sig_len = ((mbedtls_rsa_context *) ctx)->len;
+    *sig_len = mbedtls_rsa_get_len( rsa );
 
-    return( mbedtls_rsa_pkcs1_sign( (mbedtls_rsa_context *) ctx, f_rng, p_rng, MBEDTLS_RSA_PRIVATE,
+    return( mbedtls_rsa_pkcs1_sign( rsa, f_rng, p_rng, MBEDTLS_RSA_PRIVATE,
                 md_alg, (unsigned int) hash_len, hash, sig ) );
 }
 
@@ -117,10 +122,12 @@
                     unsigned char *output, size_t *olen, size_t osize,
                     int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
-    if( ilen != ((mbedtls_rsa_context *) ctx)->len )
+    mbedtls_rsa_context * rsa = (mbedtls_rsa_context *) ctx;
+
+    if( ilen != mbedtls_rsa_get_len( rsa ) )
         return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
 
-    return( mbedtls_rsa_pkcs1_decrypt( (mbedtls_rsa_context *) ctx, f_rng, p_rng,
+    return( mbedtls_rsa_pkcs1_decrypt( rsa, f_rng, p_rng,
                 MBEDTLS_RSA_PRIVATE, olen, input, output, osize ) );
 }
 
@@ -129,13 +136,14 @@
                     unsigned char *output, size_t *olen, size_t osize,
                     int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
 {
-    *olen = ((mbedtls_rsa_context *) ctx)->len;
+    mbedtls_rsa_context * rsa = (mbedtls_rsa_context *) ctx;
+    *olen = mbedtls_rsa_get_len( rsa );
 
     if( *olen > osize )
         return( MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE );
 
-    return( mbedtls_rsa_pkcs1_encrypt( (mbedtls_rsa_context *) ctx,
-                f_rng, p_rng, MBEDTLS_RSA_PUBLIC, ilen, input, output ) );
+    return( mbedtls_rsa_pkcs1_encrypt( rsa, f_rng, p_rng, MBEDTLS_RSA_PUBLIC,
+                                       ilen, input, output ) );
 }
 
 static int rsa_check_pair_wrap( const void *pub, const void *prv )