diff --git a/panda/src/vision/Sources.pp b/panda/src/vision/Sources.pp
index 1684f51dbf..c28676bf4c 100644
--- a/panda/src/vision/Sources.pp
+++ b/panda/src/vision/Sources.pp
@@ -4,6 +4,8 @@
 
 #define USE_PACKAGES opencv artoolkit
 
+#define BUILDING_DLL BUILDING_VISION
+
 #begin lib_target
   #define TARGET vision
   #define LOCAL_LIBS \