diff --git a/bin/tests/db_test.c b/bin/tests/db_test.c
index b367eeba84..0f7c64d0cf 100644
--- a/bin/tests/db_test.c
+++ b/bin/tests/db_test.c
@@ -613,10 +613,11 @@ main(int argc, char *argv[]) {
 		} else if (strstr(s, "!V") == s) {
 			DBI_CHECK(dbi);
 			v = atoi(&s[2]);
-			if (v >= dbi->rcount) {
+			if (v >= dbi->rcount || v < 0) {
 				printf("unknown open version %d\n", v);
 				continue;
-			} else if (dbi->rversions[v] == NULL) {
+			}
+			if (dbi->rversions[v] == NULL) {
 				printf("version %d is not open\n", v);
 				continue;
 			}
diff --git a/bin/tests/shutdown_test.c b/bin/tests/shutdown_test.c
index 7ccce80851..0dcf3b82c9 100644
--- a/bin/tests/shutdown_test.c
+++ b/bin/tests/shutdown_test.c
@@ -174,9 +174,13 @@ main(int argc, char *argv[]) {
 
 	RUNTIME_CHECK(isc_app_start() == ISC_R_SUCCESS);
 
-	if (argc > 1)
+	if (argc > 1) {
 		workers = atoi(argv[1]);
-	else
+		if (workers < 1)
+			workers = 1;
+		if (workers > 8192)
+			workers = 8192;
+	} else
 		workers = 2;
 	printf("%d workers\n", workers);
 
diff --git a/bin/tests/sock_test.c b/bin/tests/sock_test.c
index 8f33a7ed49..f6d2a39222 100644
--- a/bin/tests/sock_test.c
+++ b/bin/tests/sock_test.c
@@ -263,9 +263,13 @@ main(int argc, char *argv[]) {
 	isc_result_t result;
 	int pf;
 
-	if (argc > 1)
+	if (argc > 1) {
 		workers = atoi(argv[1]);
-	else
+		if (workers < 1)
+			workers = 1;
+		if (workers > 8192)
+			workers = 8192;
+	} else
 		workers = 2;
 	printf("%d workers\n", workers);
 
diff --git a/bin/tests/task_test.c b/bin/tests/task_test.c
index e3ff26b56c..2e162b6d1e 100644
--- a/bin/tests/task_test.c
+++ b/bin/tests/task_test.c
@@ -69,9 +69,13 @@ main(int argc, char *argv[]) {
 	isc_timer_t *ti1, *ti2;
 	struct isc_interval interval;
 
-	if (argc > 1)
+	if (argc > 1) {
 		workers = atoi(argv[1]);
-	else
+		if (workers < 1)
+			workers = 1;
+		if (workers > 8192)
+			workers = 8192;
+	} else
 		workers = 2;
 	printf("%d workers\n", workers);
 
diff --git a/bin/tests/timer_test.c b/bin/tests/timer_test.c
index 2825dc58e9..cb5459ccf2 100644
--- a/bin/tests/timer_test.c
+++ b/bin/tests/timer_test.c
@@ -102,9 +102,13 @@ main(int argc, char *argv[]) {
 	isc_time_t expires, now;
 	isc_interval_t interval;
 
-	if (argc > 1)
+	if (argc > 1) {
 		workers = atoi(argv[1]);
-	else
+		if (workers < 1)
+			workers = 1;
+		if (workers > 8192)
+			workers = 8192;
+	} else
 		workers = 2;
 	printf("%d workers\n", workers);