diff --git a/makefiles/vars.inc.mk b/makefiles/vars.inc.mk
index 7fc732cd1056ba3ca6bdea462e9c62232a961b76..3492bffbf0b09516691cfb179de9c75bc0ebd7d2 100644
--- a/makefiles/vars.inc.mk
+++ b/makefiles/vars.inc.mk
@@ -12,6 +12,7 @@ export CPU                   # The CPU, set by the board's Makefile.include.
 export CPU_MODEL             # The specific identifier of the used CPU, used for some CPU implementations to differentiate between different memory layouts
 export MCU                   # The MCU, set by the board's Makefile.include, or defaulted to the same value as CPU.
 export INCLUDES              # The extra include paths, set by the various Makefile.include files.
+export CXXINCLUDES           # The extra include paths for c++, set by the various Makefile.include files.
 
 export USEMODULE             # Sys Module dependencies of the application. Set in the application's Makefile.
 export USEPKG                # Pkg dependencies (third party modules) of the application. Set in the application's Makefile.