diff --git a/panda/metalibs/panda/CMakeLists.txt b/panda/metalibs/panda/CMakeLists.txt
index e212a7e60e..cd62d585c8 100644
--- a/panda/metalibs/panda/CMakeLists.txt
+++ b/panda/metalibs/panda/CMakeLists.txt
@@ -1,3 +1,4 @@
+add_definitions(-DBUILDING_PANDA)
 set(PANDA_LINK_TARGETS p3pnmimagetypes p3device)
 
 if(LINK_IN_PHYSX)