diff --git a/library/x509write_crt.c b/library/x509write_crt.c
index 56f23c9fab..d829ffe602 100644
--- a/library/x509write_crt.c
+++ b/library/x509write_crt.c
@@ -84,12 +84,14 @@ void mbedtls_x509write_crt_set_issuer_key(mbedtls_x509write_cert *ctx,
 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);
 }
 
diff --git a/library/x509write_csr.c b/library/x509write_csr.c
index 0d6f6bb1d3..75bd8f044e 100644
--- a/library/x509write_csr.c
+++ b/library/x509write_csr.c
@@ -66,6 +66,7 @@ void mbedtls_x509write_csr_set_key(mbedtls_x509write_csr *ctx, mbedtls_pk_contex
 int mbedtls_x509write_csr_set_subject_name(mbedtls_x509write_csr *ctx,
                                            const char *subject_name)
 {
+    mbedtls_asn1_free_named_data_list(&ctx->subject);
     return mbedtls_x509_string_to_names(&ctx->subject, subject_name);
 }