diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index e3bde01..0201963 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -1339,6 +1339,10 @@
  *                  See the description of the \p buflen parameter for
  *                  how to calculate the nominal length.
  *
+ * \note            If the private key was not set in \p key,
+ *                  the output is unspecified. Future versions
+ *                  may return an error in that case.
+ *
  * \param key       The private key.
  * \param buf       The output buffer for containing the binary representation
  *                  of the key.
@@ -1369,6 +1373,10 @@
 /**
  * \brief           This function exports an elliptic curve public key.
  *
+ * \note            If the public key was not set in \p key,
+ *                  the output is unspecified. Future versions
+ *                  may return an error in that case.
+ *
  * \param key       The public key.
  * \param format    The point format. This must be either
  *                  #MBEDTLS_ECP_PF_COMPRESSED or #MBEDTLS_ECP_PF_UNCOMPRESSED.
@@ -1451,6 +1459,10 @@
  *                  Each of the output parameters can be a null pointer
  *                  if you do not need that parameter.
  *
+ * \note            If the private key or the public key was not set in \p key,
+ *                  the corresponding output is unspecified. Future versions
+ *                  may return an error in that case.
+ *
  * \param key       The key pair to export from.
  * \param grp       Slot for exported ECP group.
  *                  It must either be null or point to an initialized ECP group.