diff --git a/cudd/Makefile.darwin-64 b/cudd/Makefile.darwin-64
index 61735a61..7eb6863b 100644
--- a/cudd/Makefile.darwin-64
+++ b/cudd/Makefile.darwin-64
@@ -63,7 +63,7 @@ ICFLAGS	=
 #
 #  Mac OS X (Darwin) (64-bit)
 #
-XCFLAGS	= -arch x86_64 -fPIC -DPIC -DHAVE_IEEE_754 -fno-common
+XCFLAGS	= -arch x86_64 -fPIC -DPIC -DHAVE_IEEE_754 -DSIZEOF_VOID_P=8 -DSIZEOF_LONG=8 -fno-common
 #
 #==========================