diff --git a/Doc/lib/libturtle.tex b/Doc/lib/libturtle.tex
index 6b9585f..2b329b7 100644
--- a/Doc/lib/libturtle.tex
+++ b/Doc/lib/libturtle.tex
@@ -108,7 +108,9 @@
 \end{funcdesc}
 
 \begin{funcdesc}{begin\_fill}{}
-Switch turtle into filling mode; equivalent to \code{fill(1)}.
+Switch turtle into filling mode; 
+Must eventually be followed by a corresponding end_fill() call.
+Otherwise it will be ignored.
 \versionadded{2.5}
 \end{funcdesc}