diff --git a/pandatool/src/ptloader/Sources.pp b/pandatool/src/ptloader/Sources.pp
index 69bec257d7..f56817d6a4 100644
--- a/pandatool/src/ptloader/Sources.pp
+++ b/pandatool/src/ptloader/Sources.pp
@@ -1,3 +1,5 @@
+#define USE_PACKAGES dx
+
 #begin lib_target
   #define TARGET ptloader
   #define BUILDING_DLL BUILDING_PTLOADER