diff --git a/doc/mymath.sty b/doc/mymath.sty
index 04aedf6302..738c7e9afc 100644
--- a/doc/mymath.sty
+++ b/doc/mymath.sty
@@ -28,7 +28,7 @@
   #3 & \mbox{#4}\\
   #5 & \mbox{#6}\\
   \end{array} \right.}
-\newcommand{\forkthree}[8]{
+\newcommand{\forkfour}[8]{
   \left\{
   \begin{array}{l l}
   #1 & \mbox{#2}\\