diff --git a/config.project b/config.project
index 9cb2cf3..c29e984 100644
--- a/config.project
+++ b/config.project
@@ -31,8 +31,8 @@ mb_ccenv_skip_native=
 
 # switches
 mb_default_cflags_common="-std=c99 -D_XOPEN_SOURCE=700"
-mb_default_cflags_common="$mb_default_cflags_common -I\$(PROJECT_DIR)/src/internal"
-mb_default_cflags_common="$mb_default_cflags_common -I\$(PROJECT_DIR)/include"
+mb_default_cflags_common="$mb_default_cflags_common -I\$(SOURCE_DIR)/src/internal"
+mb_default_cflags_common="$mb_default_cflags_common -I\$(SOURCE_DIR)/include"
 mb_default_cflags_common="$mb_default_cflags_common -Ibuild"
 
 mb_default_cflags_debug=