diff --git a/Doxyfile.coding.in b/Doxyfile.coding.in
index d0e9942..50355de 100644
--- a/Doxyfile.coding.in
+++ b/Doxyfile.coding.in
@@ -1485,7 +1485,7 @@
 # If a tag file is not located in the directory in which doxygen
 # is run, you must also specify the path to the tagfile here.
 
-TAGFILES = doc/libosmocore.tag=../../core/html doc/libosmogsm.tag=../../gsm/html doc/libosmovty.tag=../../vty/html doc/libosmocodec.tag=../../codec/html doc/libosmoctrl.tag=../../ctrl/html doc/libosmogb.tag=../../gb/html
+TAGFILES = doc/libosmocore.tag=../../core/html doc/libosmogsm.tag=../../gsm/html doc/libosmoisdn.tag=../../isdn/html doc/libosmovty.tag=../../vty/html doc/libosmocodec.tag=../../codec/html doc/libosmoctrl.tag=../../ctrl/html doc/libosmogb.tag=../../gb/html
 
 # When a file name is specified after GENERATE_TAGFILE, doxygen will create
 # a tag file that is based on the input files it reads.