diff --git a/doc/doxygen.conf b/doc/doxygen.conf
index a8b337f0a..fc6fd25fa 100644
--- a/doc/doxygen.conf
+++ b/doc/doxygen.conf
@@ -999,7 +999,7 @@ INCLUDE_FILE_PATTERNS  =
 # undefined via #undef or recursively expanded use the := operator 
 # instead of the = operator.
 
-PREDEFINED             = RUN_SELF_TESTS NS3_DEBUG_ENABLE
+PREDEFINED             = RUN_SELF_TESTS NS3_DEBUG_ENABLE NS3_ASSERT_ENABLE
 
 # 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.