diff --git a/cplusplus/Doxyfile.in b/cplusplus/Doxyfile.in
index 1019ff5a..db7c810a 100644
--- a/cplusplus/Doxyfile.in
+++ b/cplusplus/Doxyfile.in
@@ -263,12 +263,6 @@ TAB_SIZE               = 8
 
 ALIASES                =
 
-# This tag can be used to specify a number of word-keyword mappings (TCL only).
-# A mapping has the form "name=value". For example adding "class=itcl::class"
-# will allow you to use the command class in the itcl::class meaning.
-
-TCL_SUBST              =
-
 # Set the OPTIMIZE_OUTPUT_FOR_C tag to YES if your project consists of C sources
 # only. Doxygen will then generate output that is more tailored for C. For
 # instance, some of the names that are used will be different. The list of all