diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 7ecafa0..e45d25a 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -918,7 +918,7 @@
 all_intermediate += cert_md2.csr
 
 cert_md2.crt: cert_md2.csr
-	$(MBEDTLS_CERT_WRITE) request_file=$< serial=4 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20110212144406 not_after=20210212144406 md=MD2 version=3 output_file=$@
+	$(MBEDTLS_CERT_WRITE) request_file=$< serial=9 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20000101121212 not_after=20300101121212 md=MD2 version=3 output_file=$@
 all_final += cert_md2.crt
 
 cert_md4.csr: $(cert_md_test_key)
@@ -926,7 +926,7 @@
 all_intermediate += cert_md4.csr
 
 cert_md4.crt: cert_md4.csr
-	$(MBEDTLS_CERT_WRITE) request_file=$< serial=4 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20110212144406 not_after=20210212144406 md=MD4 version=3 output_file=$@
+	$(MBEDTLS_CERT_WRITE) request_file=$< serial=5 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20000101121212 not_after=20300101121212 md=MD4 version=3 output_file=$@
 all_final += cert_md4.crt
 
 cert_md5.csr: $(cert_md_test_key)
@@ -934,7 +934,7 @@
 all_intermediate += cert_md5.csr
 
 cert_md5.crt: cert_md5.csr
-	$(MBEDTLS_CERT_WRITE) request_file=$< serial=4 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20110212144406 not_after=20210212144406 md=MD5 version=3 output_file=$@
+	$(MBEDTLS_CERT_WRITE) request_file=$< serial=6 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20000101121212 not_after=20300101121212 md=MD5 version=3 output_file=$@
 all_final += cert_md5.crt
 
 ################################################################