diff --git a/panda/src/shader/Sources.pp b/panda/src/shader/Sources.pp
index 4d30c5dafb..9b883358df 100644
--- a/panda/src/shader/Sources.pp
+++ b/panda/src/shader/Sources.pp
@@ -1,5 +1,7 @@
 #define OTHER_LIBS interrogatedb dconfig dtoolutil dtoolbase
 
+#define BUILDING_DLL BUILDING_SHADER
+
 #begin lib_target
   #define TARGET shader
   #define LOCAL_LIBS \