diff --git a/src/core/libs/supl/asn-supl/GeneralizedTime.c b/src/core/libs/supl/asn-supl/GeneralizedTime.c
index c3e01f99e..2fd63f262 100644
--- a/src/core/libs/supl/asn-supl/GeneralizedTime.c
+++ b/src/core/libs/supl/asn-supl/GeneralizedTime.c
@@ -3,7 +3,7 @@
  * Redistribution and modifications are permitted subject to BSD license.
  */
 #define	_POSIX_PTHREAD_SEMANTICS	/* for Sun */
-#ifdef _REENTRANT
+#ifndef _REENTRANT
 #define	_REENTRANT			/* for Sun */
 #endif
 #include <asn_internal.h>