- 2, 0, 0, (SCM context, SCM sym),
- "Return the value for property @var{sym} in @var{context}.")
+ 2, 1, 0, (SCM context, SCM sym, SCM def),
+ "Return the value for property @var{sym} in @var{context}."
+ " If @var{def} is given, and property value is @code{'()},"
+ " return @var{def}.")