diff --git a/runtime/include/sandbox_functions.h b/runtime/include/sandbox_functions.h
index 3803cc2..c4aee1a 100644
--- a/runtime/include/sandbox_functions.h
+++ b/runtime/include/sandbox_functions.h
@@ -105,12 +105,15 @@ sandbox_get_priority(void *element)
 	return sandbox->absolute_deadline;
 };
 
-static inline int64_t
+static inline uint64_t
 sandbox_get_srsf_priority(void *element)
 {
 	struct sandbox *sandbox = (struct sandbox *)element;
 	uint64_t now = __getcycles();
         int64_t remaining_slack = sandbox->remaining_slack - (now - sandbox->last_update_timestamp);
+	if (remaining_slack < 0) {
+		return 0;
+	}
         return remaining_slack;
 };
 
diff --git a/runtime/src/global_request_scheduler_minheap.c b/runtime/src/global_request_scheduler_minheap.c
index 94f45d8..f0c731b 100644
--- a/runtime/src/global_request_scheduler_minheap.c
+++ b/runtime/src/global_request_scheduler_minheap.c
@@ -71,12 +71,15 @@ sandbox_request_get_priority_fn(void *element)
 	return sandbox_request->absolute_deadline;
 };
 
-int64_t
+uint64_t
 sandbox_request_get_priority_srsf_fn(void *element)
 {
 	struct sandbox_request *sandbox_request = (struct sandbox_request *)element;
 	uint64_t now = __getcycles();	
 	int64_t remaining_slack = sandbox_request->remaining_slack - (now - sandbox_request->last_update_timestamp);
+	if (remaining_slack < 0) {
+		return 0;
+	}
 	return remaining_slack;
 };