Index: head/contrib/netbsd-tests/usr.bin/grep/t_grep.sh
===================================================================
--- head/contrib/netbsd-tests/usr.bin/grep/t_grep.sh
+++ head/contrib/netbsd-tests/usr.bin/grep/t_grep.sh
@@ -517,6 +517,28 @@
 	atf_check -o empty grep -q -A 1 -e "B" test1
 	atf_check -o empty grep -q -C 1 -e "B" test1
 }
+
+atf_test_case badcontext
+badcontext_head()
+{
+	atf_set "descr" "Check for handling of invalid context arguments"
+}
+badcontext_body()
+{
+	printf "A\nB\nC\n" > test1
+
+	atf_check -s not-exit:0 -e ignore grep -A "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -B "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -C "-1" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -A "B" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -B "B" "B" test1
+
+	atf_check -s not-exit:0 -e ignore grep -C "B" "B" test1
+}
 # End FreeBSD
 
 atf_init_test_cases()
@@ -551,5 +573,6 @@
 	atf_add_test_case egrep_sanity
 	atf_add_test_case grep_sanity
 	atf_add_test_case grep_nomatch_flags
+	atf_add_test_case badcontext
 # End FreeBSD
 }
Index: head/usr.bin/grep/grep.h
===================================================================
--- head/usr.bin/grep/grep.h
+++ head/usr.bin/grep/grep.h
@@ -115,7 +115,7 @@
 		 bflag, cflag, hflag, iflag, lflag, mflag, nflag, oflag,
 		 qflag, sflag, vflag, wflag, xflag;
 extern bool	 dexclude, dinclude, fexclude, finclude, lbflag, nullflag;
-extern unsigned long long Aflag, Bflag;
+extern long long Aflag, Bflag;
 extern long long mcount;
 extern long long mlimit;
 extern char	 fileeol;
Index: head/usr.bin/grep/grep.c
===================================================================
--- head/usr.bin/grep/grep.c
+++ head/usr.bin/grep/grep.c
@@ -108,8 +108,8 @@
 char	 re_error[RE_ERROR_BUF + 1];
 
 /* Command-line flags */
-unsigned long long Aflag;	/* -A x: print x lines trailing each match */
-unsigned long long Bflag;	/* -B x: print x lines leading each match */
+long long Aflag;	/* -A x: print x lines trailing each match */
+long long Bflag;	/* -B x: print x lines leading each match */
 bool	 Hflag;		/* -H: always print file name */
 bool	 Lflag;		/* -L: only show names of files with no matches */
 bool	 bflag;		/* -b: show block numbers for each match */
@@ -351,7 +351,7 @@
 	char **aargv, **eargv, *eopts;
 	char *ep;
 	const char *pn;
-	unsigned long long l;
+	long long l;
 	unsigned int aargc, eargc, i;
 	int c, lastc, needpattern, newarg, prevoptind;
 
@@ -438,10 +438,11 @@
 		case '5': case '6': case '7': case '8': case '9':
 			if (newarg || !isdigit(lastc))
 				Aflag = 0;
-			else if (Aflag > LLONG_MAX / 10) {
+			else if (Aflag > LLONG_MAX / 10 - 1) {
 				errno = ERANGE;
 				err(2, NULL);
 			}
+
 			Aflag = Bflag = (Aflag * 10) + (c - '0');
 			break;
 		case 'C':
@@ -454,14 +455,17 @@
 			/* FALLTHROUGH */
 		case 'B':
 			errno = 0;
-			l = strtoull(optarg, &ep, 10);
-			if (((errno == ERANGE) && (l == ULLONG_MAX)) ||
-			    ((errno == EINVAL) && (l == 0)))
+			l = strtoll(optarg, &ep, 10);
+			if (errno == ERANGE || errno == EINVAL)
 				err(2, NULL);
 			else if (ep[0] != '\0') {
 				errno = EINVAL;
 				err(2, NULL);
+			} else if (l < 0) {
+				errno = EINVAL;
+				err(2, "context argument must be non-negative");
 			}
+
 			if (c == 'A')
 				Aflag = l;
 			else if (c == 'B')
Index: head/usr.bin/grep/queue.c
===================================================================
--- head/usr.bin/grep/queue.c
+++ head/usr.bin/grep/queue.c
@@ -49,7 +49,7 @@
 };
 
 static STAILQ_HEAD(, qentry)	queue = STAILQ_HEAD_INITIALIZER(queue);
-static unsigned long long	count;
+static long long		count;
 
 static struct qentry	*dequeue(void);
 
Index: head/usr.bin/grep/util.c
===================================================================
--- head/usr.bin/grep/util.c
+++ head/usr.bin/grep/util.c
@@ -196,11 +196,12 @@
 procfile(const char *fn)
 {
 	struct parsec pc;
+	long long tail;
 	struct file *f;
 	struct stat sb;
 	struct str *ln;
 	mode_t s;
-	int c, last_outed, t, tail;
+	int c, last_outed, t;
 	bool doctx, printmatch, same_file;
 
 	if (strcmp(fn, "-") == 0) {