diff --git a/makefiles/app_dirs.inc.mk b/makefiles/app_dirs.inc.mk
index 4179f99f90..bdf45ec995 100644
--- a/makefiles/app_dirs.inc.mk
+++ b/makefiles/app_dirs.inc.mk
@@ -17,6 +17,7 @@ APPLICATION_DIRS :=                   \
     tests/drivers                     \
     tests/periph                      \
     tests/pkg                         \
+    tests/sys                         \
     #
 
 APPLICATION_DIRS := $(addprefix $(RIOTBASE)/,$(APPLICATION_DIRS))