diff --git a/SAMv1.tex b/SAMv1.tex
index 97b8e74c3..f2c1f99ad 100644
--- a/SAMv1.tex
+++ b/SAMv1.tex
@@ -636,9 +636,13 @@ \subsection{The alignment section: mandatory fields}\label{sec:alnrecord}
 \item {\sf QUAL}: ASCII of base QUALity plus 33 (same as the quality
   string in the Sanger FASTQ format). A base quality is the phred-scaled
   base error probability which equals $-10\log_{10}\Pr\{\mbox{base is
-    wrong}\}$. This field can be a `*' when quality is not stored. If
-  not a `*', {\sf SEQ} must not be a `*' and the length of the quality string
-  ought to equal the length of {\sf SEQ}.
+    wrong}\}$.
+  This field can be a `*' when quality is not stored.\footnote{Note an
+  ambiguity exists for the unlikely case of a non-`*' sequence of length 1
+  with base quality 9 (ASCII `*').  Given the ambiguity, the quality
+  should always deemed to be unavailable in this scenario.}
+  If not a `*', {\sf SEQ} must not be a `*' and the length of the quality
+  string ought to equal the length of {\sf SEQ}.
 \end{enumerate}
 
 \subsection{The alignment section: optional fields}\label{sec:alnaux}