diff --git a/html/user/submit_rpc_handler.php b/html/user/submit_rpc_handler.php
index 9ce4f0d8ac..32b7a338e6 100644
--- a/html/user/submit_rpc_handler.php
+++ b/html/user/submit_rpc_handler.php
@@ -160,7 +160,6 @@ function xml_get_jobs($r) {
 }
 
 function submit_batch($r) {
-    print_r($r);
     $app = get_app($r);
     list($user, $user_submit) = authenticate_user($r, $app);
     $template = read_input_template($app);
@@ -201,7 +200,7 @@ function submit_batch($r) {
         }
     }
     $cmd = "cd ../../bin; ./adjust_user_priority --user $user->id --flops $total_flops --app $app->name";
-    $x = system($cmd);
+    $x = exec($cmd);
     if (!is_numeric($x) || (double)$x == 0) {
         xml_error(-1, "$cmd returned $x");
     }
diff --git a/tools/backend_lib.cpp b/tools/backend_lib.cpp
index 1aa1db3ff7..b9757e32b7 100644
--- a/tools/backend_lib.cpp
+++ b/tools/backend_lib.cpp
@@ -622,6 +622,9 @@ double user_priority_delta(
     double total_quota,
     double project_flops
 ) {
+    if (total_quota == 0) return 0;
+    if (project_flops == 0) return 0;
+
     double runtime = flop_count / project_flops;
     double share = us.quota / total_quota;
 #if 0