diff --git a/util.cpp b/util.cpp
index deae91b..9bc6704 100644
--- a/util.cpp
+++ b/util.cpp
@@ -1411,7 +1411,7 @@ out:
 	return ret;
 }
 
-extern time_t g_work_time;
+extern volatile time_t g_work_time;
 static bool stratum_set_difficulty(struct stratum_ctx *sctx, json_t *params)
 {
 	double diff;