diff --git a/tools/Doxyfile b/tools/Doxyfile
index 17970f61..0b3ad94d 100644
--- a/tools/Doxyfile
+++ b/tools/Doxyfile
@@ -230,12 +230,6 @@ 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