diff --git a/projects/xnu/build.sh b/projects/xnu/build.sh
index 715e32bd2..c296a3369 100755
--- a/projects/xnu/build.sh
+++ b/projects/xnu/build.sh
@@ -15,8 +15,8 @@
 #
 ################################################################################
 
-mkdir build
-cd build
+mkdir $SRC/build
+cd $SRC/build
 
 cmake -GNinja $SRC/SockFuzzer
 ninja
diff --git a/projects/xnu/project.yaml b/projects/xnu/project.yaml
index e0d883189..c9abb09bd 100644
--- a/projects/xnu/project.yaml
+++ b/projects/xnu/project.yaml
@@ -7,3 +7,4 @@ fuzzing_engines:
   - honggfuzz
 sanitizers:
   - address
+  - undefined