diff --git a/doc/GTF.asc b/doc/GTF.asc
index 5578a59..2f703dd 100644
--- a/doc/GTF.asc
+++ b/doc/GTF.asc
@@ -840,4 +840,4 @@ description override the corresponding font table in the font, means that a name
 table in an external binary description must be complete, including all the
 strings from the original font.
 
-include::OpCodes.txt[]
+include::OpCodes.asc[]