diff --git a/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h b/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
index a45d18e8ab2..93f1855b390 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
+++ b/sys/cddl/contrib/opensolaris/uts/common/sys/isa_defs.h
@@ -525,7 +525,9 @@ extern "C" {
 /*
  * Define the appropriate "implementation choices".
  */
+#if !defined(_ILP32)
 #define	_ILP32
+#endif
 #if !defined(_I32LPx) && defined(_KERNEL)
 #define	_I32LPx
 #endif