diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6dbf2b49..f95b0e86 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,4 @@
-# Generated by `boostdep --cmake serialization`
-# Copyright 2020 Peter Dimov
+# Copyright 2020, 2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # https://www.boost.org/LICENSE_1_0.txt
 
@@ -97,12 +96,14 @@ target_link_libraries(boost_wserialization PUBLIC boost_serialization)
 
 target_compile_definitions(boost_serialization
   PUBLIC BOOST_SERIALIZATION_NO_LIB
-  PRIVATE BOOST_SERIALIZATION_SOURCE
+  # Source files already define BOOST_SERIALIZATION_SOURCE
+  # PRIVATE BOOST_SERIALIZATION_SOURCE
 )
 
 target_compile_definitions(boost_wserialization
   PUBLIC BOOST_SERIALIZATION_NO_LIB
-  PRIVATE BOOST_SERIALIZATION_SOURCE
+  # Source files already define BOOST_SERIALIZATION_SOURCE
+  # PRIVATE BOOST_SERIALIZATION_SOURCE
 )
 
 if(BUILD_SHARED_LIBS)