diff --git a/library/ssl_msg.c b/library/ssl_msg.c
index 3547f67..20501c9 100644
--- a/library/ssl_msg.c
+++ b/library/ssl_msg.c
@@ -5873,6 +5873,10 @@
         return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
     }
 
+    /*
+     * The server may receive early data only while waiting for the End of
+     * Early Data handshake message.
+     */
     if ((ssl->state != MBEDTLS_SSL_END_OF_EARLY_DATA) ||
         (ssl->in_offt == NULL)) {
         return MBEDTLS_ERR_SSL_CANNOT_READ_EARLY_DATA;