diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 56f23c9..d829ffe 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -84,12 +84,14 @@
 int mbedtls_x509write_crt_set_subject_name(mbedtls_x509write_cert *ctx,
                                            const char *subject_name)
 {
+    mbedtls_asn1_free_named_data_list(&ctx->subject);
     return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
 }
 
 int mbedtls_x509write_crt_set_issuer_name(mbedtls_x509write_cert *ctx,
                                           const char *issuer_name)
 {
+    mbedtls_asn1_free_named_data_list(&ctx->issuer);
     return mbedtls_x509_string_to_names(&ctx->issuer, issuer_name);
 }