diff --git a/docs/yap.tex b/docs/yap.tex
index 4ecbbfdf5..085fc9030 100644
--- a/docs/yap.tex
+++ b/docs/yap.tex
@@ -7484,7 +7484,7 @@ Interface with @var{tmpnam}: create an unique file and unify its name
 with @var{File}.
 
 @item
-exec(+@var{Command},[+@var{InputStream},+@var{OutputStream},,+@var{ErrorStream},
+exec(+@var{Command},[+@var{InputStream},+@var{OutputStream},+@var{ErrorStream}],
 -@var{Status})
 @findex  exec/3
 @syindex exec/3