diff --git a/pd/src/x_vexp.h b/pd/src/x_vexp.h
index 608a64a486f9c94eb934fd8ed54b256d509e540a..bc3b4204074e9f319dc087abcb62b67912ae3313 100644
--- a/pd/src/x_vexp.h
+++ b/pd/src/x_vexp.h
@@ -5,9 +5,9 @@
 /* "expr" was written by Shahrokh Yadegari c. 1989. -msp */
 /* "expr~" and "fexpr~" conversion by Shahrokh Yadegari c. 1999,2000 */
 
-#define MSP
-#ifdef PD
-#undef MSP
+#define PD 1
+#ifdef MSP
+#undef PD
 #endif
 
 #ifdef PD