diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 340d951..9c7a95d 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -972,12 +972,15 @@
 
 server1.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
 	$(MBEDTLS_CERT_WRITE) request_file=server1.req.sha256 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) version=1 not_before=20190210144406 not_after=20290210144406 md=SHA1 version=3 output_file=$@
-server1.long_serial.crt: server1.long_serial.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
+server1.long_serial.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
 	echo "112233445566778899aabbccddeeff0011223344" > test-ca.server1.tmp.serial
 	$(OPENSSL) ca -in server1.req.sha256 -key PolarSSLTest -config test-ca.server1.test_serial.opensslconf -notext -batch -out $@
-server1.80serial.crt: server1.long_serial.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
+server1.80serial.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
 	echo "8011223344" > test-ca.server1.tmp.serial
 	$(OPENSSL) ca -in server1.req.sha256 -key PolarSSLTest -config test-ca.server1.test_serial.opensslconf -notext -batch -out $@
+server1.long_serial_FF.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
+	echo "ffffffffffffffffffffffffffffffff" > test-ca.server1.tmp.serial
+	$(OPENSSL) ca -in server1.req.sha256 -key PolarSSLTest -config test-ca.server1.test_serial.opensslconf -notext -batch -out $@
 server1.noauthid.crt: server1.key server1.req.sha256 $(test_ca_crt) $(test_ca_key_file_rsa)
 	$(MBEDTLS_CERT_WRITE) request_file=server1.req.sha256 issuer_crt=$(test_ca_crt) issuer_key=$(test_ca_key_file_rsa) issuer_pwd=$(test_ca_pwd_rsa) not_before=20190210144406 not_after=20290210144406 md=SHA1 authority_identifier=0 version=3 output_file=$@
 server1.crt.der: server1.crt
diff --git a/tests/data_files/server1.long_serial_FF.crt b/tests/data_files/server1.long_serial_FF.crt
new file mode 100644
index 0000000..8094fd7
--- /dev/null
+++ b/tests/data_files/server1.long_serial_FF.crt
@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/suites/test_suite_x509write.data b/tests/suites/test_suite_x509write.data
index b5e07f5..885ba00 100644
--- a/tests/suites/test_suite_x509write.data
+++ b/tests/suites/test_suite_x509write.data
@@ -150,6 +150,10 @@
 depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
 x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"8011223344":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.80serial.crt":0:0:"data_files/test-ca.crt"
 
+Certificate write check Server1 SHA1, All 0xFF full length serial
+depends_on:MBEDTLS_RSA_C:MBEDTLS_PKCS1_V15:MBEDTLS_DES_C:MBEDTLS_CIPHER_MODE_CBC:MBEDTLS_HAS_ALG_MD5_VIA_MD_OR_PSA_BASED_ON_USE_PSA
+x509_crt_check:"data_files/server1.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=PolarSSL Test CA":"ffffffffffffffffffffffffffffffff":"20190210144406":"20290210144406":MBEDTLS_MD_SHA1:0:0:"NULL":0:0:1:-1:"data_files/server1.long_serial_FF.crt":0:0:"data_files/test-ca.crt"
+
 Certificate write check Server5 ECDSA
 depends_on:MBEDTLS_HAS_ALG_SHA_256_VIA_MD_OR_PSA_BASED_ON_USE_PSA:MBEDTLS_ECDSA_C:MBEDTLS_ECDSA_DETERMINISTIC:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 x509_crt_check:"data_files/server5.key":"":"C=NL,O=PolarSSL,CN=PolarSSL Server 1":"data_files/test-ca2.key":"PolarSSLTest":"C=NL,O=PolarSSL,CN=Polarssl Test EC CA":"01":"20190210144406":"20290210144406":MBEDTLS_MD_SHA256:0:0:"NULL":0:0:1:-1:"data_files/server5.crt":0:0:"data_files/test-ca2.crt"