diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 909258c..b616a73 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -126,6 +126,7 @@
 #define MBEDTLS_ERR_SSL_CONTINUE_PROCESSING               -0x6580  /**< Internal-only message signaling that further message-processing should be done */
 #define MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS                 -0x6500  /**< The asynchronous operation is not completed yet. */
 #define MBEDTLS_ERR_SSL_EARLY_MESSAGE                     -0x6480  /**< Internal-only message signaling that a message arrived early. */
+#define MBEDTLS_ERR_SSL_UNEXPECTED_CID                    -0x6000  /**< An encrypted DTLS-frame with an unexpected CID was received. */
 #define MBEDTLS_ERR_SSL_CRYPTO_IN_PROGRESS                -0x7000  /**< A cryptographic operation is in progress. Try again later. */
 
 /*