diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 08794e34c786..83dd537c6501 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -510,7 +510,7 @@ struct ksegrp {
 #define	kg_startcopy	kg_endzero
 	u_char		kg_pri_class;	/* (j) Scheduling class. */
 	u_char		kg_user_pri;	/* (j) User pri from estcpu and nice. */
-	char		kg_nice;	/* (c + j) Process "nice" value. */
+	signed char	kg_nice;	/* (c + j) Process "nice" value. */
 #define	kg_endcopy kg_numthreads
 	int		kg_numthreads;	/* (j) Num threads in total. */
 	int		kg_kses;	/* (j) Num KSEs in group. */
diff --git a/sys/sys/user.h b/sys/sys/user.h
index a52610f2680f..3524cce3043f 100644
--- a/sys/sys/user.h
+++ b/sys/sys/user.h
@@ -143,7 +143,7 @@ struct kinfo_proc {
 	long	ki_kiflag;		/* KI_* flags (below) */
 	int	ki_traceflag;		/* Kernel trace points */
 	char	ki_stat;		/* S* process status */
-	char	ki_nice;		/* Process "nice" value */
+	signed char ki_nice;		/* Process "nice" value */
 	char	ki_lock;		/* Process lock (prevent swap) count */
 	char	ki_rqindex;		/* Run queue index */
 	u_char	ki_oncpu;		/* Which cpu we are on */