diff --git a/Doc/lib/libtypes.tex b/Doc/lib/libtypes.tex
index dfe1ecb0fcc..33d1b15efb1 100644
--- a/Doc/lib/libtypes.tex
+++ b/Doc/lib/libtypes.tex
@@ -118,7 +118,7 @@ Notes:
 \item[(1)]
 \code{<>} and \code{!=} are alternate spellings for the same operator.
 (I couldn't choose between \ABC{} and \C{}! :-)
-\indexii{\ABC{}}{language}
+\indexii{ABC@\ABC{}}{language}
 \indexii{\C{}}{language}
 
 \end{description}
diff --git a/Doc/libtypes.tex b/Doc/libtypes.tex
index dfe1ecb0fcc..33d1b15efb1 100644
--- a/Doc/libtypes.tex
+++ b/Doc/libtypes.tex
@@ -118,7 +118,7 @@ Notes:
 \item[(1)]
 \code{<>} and \code{!=} are alternate spellings for the same operator.
 (I couldn't choose between \ABC{} and \C{}! :-)
-\indexii{\ABC{}}{language}
+\indexii{ABC@\ABC{}}{language}
 \indexii{\C{}}{language}
 
 \end{description}