diff --git a/sys/sys/time.h b/sys/sys/time.h
index 1a8515add0f9..38b0ffcdb5be 100644
--- a/sys/sys/time.h
+++ b/sys/sys/time.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.23 1998/04/04 13:26:16 phk Exp $
+ * $Id: time.h,v 1.24 1998/04/06 08:26:08 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -198,7 +198,10 @@ struct timecounter {
 
 #ifndef KERNEL			/* NetBSD/OpenBSD compatable interfaces */
 
-#define	timerclear(tvp)		(tvp)->tv_sec = (tvp)->tv_usec = 0
+#define	timerclear(tvp)							\
+	do {								\
+		(tvp)->tv_sec = (tvp)->tv_usec = 0;			\
+	} while(0)
 #define	timerisset(tvp)		((tvp)->tv_sec || (tvp)->tv_usec)
 #define	timercmp(tvp, uvp, cmp)					\
 	(((tvp)->tv_sec == (uvp)->tv_sec) ?				\
diff --git a/sys/sys/timetc.h b/sys/sys/timetc.h
index 1a8515add0f9..38b0ffcdb5be 100644
--- a/sys/sys/timetc.h
+++ b/sys/sys/timetc.h
@@ -31,7 +31,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)time.h	8.5 (Berkeley) 5/4/95
- * $Id: time.h,v 1.23 1998/04/04 13:26:16 phk Exp $
+ * $Id: time.h,v 1.24 1998/04/06 08:26:08 phk Exp $
  */
 
 #ifndef _SYS_TIME_H_
@@ -198,7 +198,10 @@ struct timecounter {
 
 #ifndef KERNEL			/* NetBSD/OpenBSD compatable interfaces */
 
-#define	timerclear(tvp)		(tvp)->tv_sec = (tvp)->tv_usec = 0
+#define	timerclear(tvp)							\
+	do {								\
+		(tvp)->tv_sec = (tvp)->tv_usec = 0;			\
+	} while(0)
 #define	timerisset(tvp)		((tvp)->tv_sec || (tvp)->tv_usec)
 #define	timercmp(tvp, uvp, cmp)					\
 	(((tvp)->tv_sec == (uvp)->tv_sec) ?				\