diff --git a/src/timedata.cpp b/src/timedata.cpp
index a803b2fc872..d484a1b0d6a 100644
--- a/src/timedata.cpp
+++ b/src/timedata.cpp
@@ -17,7 +17,7 @@
 
 
 static CCriticalSection cs_nTimeOffset;
-static int64_t nTimeOffset = 0;
+static int64_t nTimeOffset GUARDED_BY(cs_nTimeOffset) = 0;
 
 /**
  * "Never go to sea with two chronometers; take one or three."