diff --git a/common/StatusVector.cpp b/common/StatusVector.cpp
index 112d60d5..fb68a0cd 100644
--- a/common/StatusVector.cpp
+++ b/common/StatusVector.cpp
@@ -52,10 +52,12 @@ std::optional<float> StatusVector::GetElement(uint32_t id) const {
 }
 
 size_t StatusVector::GetImageNumber() const {
+    std::unique_lock ul(m);
     return content.size();
 }
 
 bool StatusVector::empty() const {
+    std::unique_lock ul(m);
     return count == 0;
 }