diff --git a/doc/scsh-manual/strings.tex b/doc/scsh-manual/strings.tex
index a5a58e4..ecac6b6 100644
--- a/doc/scsh-manual/strings.tex
+++ b/doc/scsh-manual/strings.tex
@@ -35,7 +35,7 @@ The code uses Henry Spencer's regular expression package.
     Is the object a regular expression match?
 \end{defundesc}
 
-\begin{defundesc} {match:start} {match [match-number]} \fixnum
+\begin{defundesc} {match:start} {match [match-number]} {{\fixnum} or false}
     Returns the start position of the match denoted by \var{match-number}.
     The whole regexp is 0.  Each further number represents positions
     enclosed by \ex{(\ldots)} sections. \var{Match-number} defaults to 0.
@@ -54,9 +54,10 @@ The code uses Henry Spencer's regular expression package.
     \ex{match:end} returns {\sharpf}.
 \end{defundesc}
 
-\begin{defundesc} {match:substring} {match [match-number]} \str
+\begin{defundesc} {match:substring} {match [match-number]} {{\str} or false}
     Returns the substring matched by match \var{match-number}.
     \var{Match-number} defaults to 0 (the whole match).
+    If there was no match, returns false.
 \end{defundesc}
 
 Regular expression matching compiles patterns into special data