diff --git a/protocol/protocol.tex b/protocol/protocol.tex
index b3069b77..2e5a0fcf 100644
--- a/protocol/protocol.tex
+++ b/protocol/protocol.tex
@@ -3866,8 +3866,9 @@ Incorrect UTF-8-encoded byte sequences should be displayed as replacement charac
 
 In the latter case, the contents of the \memo{} \SHOULDNOT be displayed. A start byte
 of $\hexint{F5}$ is reserved for use by automated software by private agreement.
-A start byte of $\hexint{F6}$ or greater is reserved for use in future \Zcash
-protocol extensions.
+A start byte of $\hexint{F6}$ followed by $511$ $\hexint{00}$ bytes means ``no memo''.
+A start byte of $\hexint{F6}$ followed by anything else, or a start byte of $\hexint{F7}$
+or greater, are reserved for use in future \Zcash protocol extensions.
 }
 
 \introlist
@@ -5504,6 +5505,8 @@ The errors in the proof of Ledger Indistinguishability mentioned in
 \begin{itemize}
     \item Specify the $100000$-byte limit on \transaction size.
           (The implementation in \zcashd was as intended.)
+    \item Specify that $\hexint{F6}$ followed by $511$ zero bytes encodes an
+          empty \memo.
     \item Rename $\mathsf{clamp}$ to $\mathsf{bound}$ and
           $\mathsf{ActualTimespanClamped}$ to $\ActualTimespanBounded$
           in the difficulty adjustment algorithm, to avoid a name