diff --git a/Documentation/Doxyfile.in b/Documentation/Doxyfile.in
index 5f4847523c53..fa8d744b93ae 100644
--- a/Documentation/Doxyfile.in
+++ b/Documentation/Doxyfile.in
@@ -244,12 +244,6 @@ ALIASES                = "context=\xrefitem context \"Thread Safety\" \"Thread S
 ALIASES               += "threadbound=\ref thread-bound \"thread-bound\""
 ALIASES               += "threadsafe=\ref thread-safe \"thread-safe\""
 
-# 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