diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 19df51e..da5ff35 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -283,7 +283,7 @@
  * \param usage_oid Intended usage (eg MBEDTLS_OID_SERVER_AUTH or MBEDTLS_OID_CLIENT_AUTH).
  * \param usage_len Length of usage_oid (eg given by MBEDTLS_OID_SIZE()).
  *
- * \return         0 is this use of the certificate is allowed,
+ * \return         0 if this use of the certificate is allowed,
  *                 MBEDTLS_ERR_X509_BAD_INPUT_DATA if not.
  *
  * \note           Usually only makes sense on leaf certificates.
@@ -544,7 +544,7 @@
  * \param f_rng     RNG function (for signature, see note)
  * \param p_rng     RNG parameter
  *
- * \return          0 successful, or a specific error code
+ * \return          0 if successful, or a specific error code
  *
  * \note            f_rng may be NULL if RSA is used for signature and the
  *                  signature is made offline (otherwise f_rng is desirable