diff --git a/doc/ref/web.texi b/doc/ref/web.texi
index d98f1bb..795e2c9 100644
--- a/doc/ref/web.texi
+++ b/doc/ref/web.texi
@@ -349,7 +349,7 @@ parsing and serialization procedures.  If a header is unknown, its
 string name is simply its symbol name in title-case.
 
 @deffn {Scheme Procedure} known-header? sym
-Return @code{#t} iff @var{sym} is a known header, with associated
+Return @code{#t} if @var{sym} is a known header, with associated
 parsers and serialization procedures.
 @end deffn
 
@@ -398,7 +398,7 @@ HTTP stack like this:
 @end example
 
 @deffn {Scheme Procedure} valid-header? sym val
-Return a true value iff @var{val} is a valid Scheme value for the header
+Return a true value if @var{val} is a valid Scheme value for the header
 with name @var{sym}.
 @end deffn