diff --git a/doxygen.cfg b/doxygen.cfg
index 2a28300d55..9fd5c87764 100644
--- a/doxygen.cfg
+++ b/doxygen.cfg
@@ -990,7 +990,7 @@ INCLUDE_FILE_PATTERNS  =
 # undefined via #undef or recursively expanded use the := operator 
 # instead of the = operator.
 
-PREDEFINED             = 
+PREDEFINED             = UNITTESTS NFQ IPFW HAVE_PFRING HAVE_AF_PACKET PRELUDE
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then 
 # this tag can be used to specify a list of macro names that should be expanded. 
@@ -1228,3 +1228,6 @@ DOT_CLEANUP            = YES
 # used. If set to NO the values of all tags below this one will be ignored.
 
 SEARCHENGINE           = YES 
+
+# Parallel graph generation: 0 to auto detect
+DOT_NUM_THREADS = 0