diff --git a/tests/suites/test_suite_ssl.function b/tests/suites/test_suite_ssl.function
index 1dec18d..39825ed 100644
--- a/tests/suites/test_suite_ssl.function
+++ b/tests/suites/test_suite_ssl.function
@@ -1052,6 +1052,12 @@
                                int buf_len, int *written,
                                const int expected_fragments)
 {
+    /* Verify that calling mbedtls_ssl_write with a NULL buffer and zero length is
+     * a valid no-op for TLS connections. */
+    if (ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
+        TEST_ASSERT(mbedtls_ssl_write(ssl, NULL, 0) == 0);
+    }
+
     int ret = mbedtls_ssl_write(ssl, buf + *written, buf_len - *written);
     if (ret > 0) {
         *written += ret;
@@ -1090,6 +1096,12 @@
                               int buf_len, int *read,
                               int *fragments, const int expected_fragments)
 {
+    /* Verify that calling mbedtls_ssl_write with a NULL buffer and zero length is
+     * a valid no-op for TLS connections. */
+    if (ssl->conf->transport != MBEDTLS_SSL_TRANSPORT_DATAGRAM) {
+        TEST_ASSERT(mbedtls_ssl_read(ssl, NULL, 0) == 0);
+    }
+
     int ret = mbedtls_ssl_read(ssl, buf + *read, buf_len - *read);
     if (ret > 0) {
         (*fragments)++;