diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 3ec55a5..41dfe87 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -177,7 +177,7 @@
     memset( buf, 0, sizeof(buf) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->subject_key ) );
 
-    ret = mbedtls_sha1_ext( buf + sizeof( buf ) - len, len,
+    ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
                             buf + sizeof( buf ) - 20 );
     if( ret != 0 )
         return( ret );
@@ -202,7 +202,7 @@
     memset( buf, 0, sizeof(buf) );
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, ctx->issuer_key ) );
 
-    ret = mbedtls_sha1_ext( buf + sizeof( buf ) - len, len,
+    ret = mbedtls_sha1_ret( buf + sizeof( buf ) - len, len,
                             buf + sizeof( buf ) - 20 );
     if( ret != 0 )
         return( ret );