diff --git a/jobs.c b/jobs.c
index 86f78b9..a6c6dd0 100755
--- a/jobs.c
+++ b/jobs.c
@@ -1585,7 +1585,7 @@ void s_wait_running_job(int s, int jobid) {
 }
 
 void s_set_max_slots(int new_max_slots) {
-    if (new_max_slots > 0)
+    if (new_max_slots >= 0)  /* -S 0 lets active jobs end without starting new ones. */
         max_slots = new_max_slots;
     else
         warning("Received new_max_slots=%i", new_max_slots);
diff --git a/main.c b/main.c
index 1195e63..1958ccd 100755
--- a/main.c
+++ b/main.c
@@ -290,8 +290,8 @@ void parse_opts(int argc, char **argv) {
             case 'S':
                 command_line.request = c_SET_MAX_SLOTS;
                 command_line.max_slots = atoi(optarg);
-                if (command_line.max_slots < 1) {
-                    fprintf(stderr, "You should set at minimum 1 slot.\n");
+                if (command_line.max_slots < 0) { /* -S 0 lets active jobs end without starting new ones. */
+                    fprintf(stderr, "You should set to 0 or more slots.\n"); /* was: You should set at minimum 1 slot.\n */
                     exit(-1);
                 }
                 break;