diff --git a/sys/kern/kern_ntptime.c b/sys/kern/kern_ntptime.c
index 815a26182096..f4071219c951 100644
--- a/sys/kern/kern_ntptime.c
+++ b/sys/kern/kern_ntptime.c
@@ -73,7 +73,13 @@ typedef int64_t l_fp;
 #define L_MPY(v, a)	((v) *= (a))
 #define L_CLR(v)	((v) = 0)
 #define L_ISNEG(v)	((v) < 0)
-#define L_LINT(v, a)	((v) = (int64_t)(a) << 32)
+#define L_LINT(v, a) \
+	do { \
+		if ((a) < 0) \
+			((v) = -((int64_t)(-(a)) << 32)); \
+		else \
+			((v) = (int64_t)(a) << 32); \
+	} while (0)
 #define L_GINT(v)	((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
 
 /*