diff --git a/ChangeLog b/ChangeLog
index acece75..912473e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -78,6 +78,8 @@
      rejected in some applications, e.g. some versions of Firefox, curl
      and GnuTLS. Reported in #1033 by Moschn. Fix contributed by
      Thomas-Dee in #1641.
+   * Improve documentation of mbedtls_ssl_get_verify_result().
+     Fixes #517 reported by github-monoculture.
 
 = mbed TLS 2.13.1 branch released 2018-09-06
 
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index e8f664a..55b206f 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2774,13 +2774,14 @@
 /**
  * \brief          Return the result of the certificate verification
  *
- * \param ssl      SSL context
+ * \param ssl      The SSL context to use.
  *
- * \return         0 if successful,
- *                 -1 if result is not available (eg because the handshake was
- *                 aborted too early), or
- *                 a combination of BADCERT_xxx and BADCRL_xxx flags, see
- *                 x509.h
+ * \return         \c 0 if the certificate verification was successful.
+ * \return         \c -1u if the result is not available. This may happen
+ *                 e.g. if the handshake aborts early, or a verification
+ *                 callback returned a fatal error.
+ * \return         A bitwise combination of \c MBEDTLS_X509_BADCERT_XXX
+ *                 and \c MBEDTLS_X509_BADCRL_XXX failure flags; see x509.h.
  */
 uint32_t mbedtls_ssl_get_verify_result( const mbedtls_ssl_context *ssl );