diff --git a/libs/sensor/Sensor.cpp b/libs/sensor/Sensor.cpp
index 139987e..abc9103 100644
--- a/libs/sensor/Sensor.cpp
+++ b/libs/sensor/Sensor.cpp
@@ -577,7 +577,8 @@
     uint32_t len = static_cast<uint32_t>(string8.length());
     FlattenableUtils::write(buffer, size, len);
     memcpy(static_cast<char*>(buffer), string8.string(), len);
-    FlattenableUtils::advance(buffer, size, FlattenableUtils::align<4>(len));
+    FlattenableUtils::advance(buffer, size, len);
+    size -= FlattenableUtils::align<4>(buffer);
 }
 
 bool Sensor::unflattenString8(void const*& buffer, size_t& size, String8& outputString8) {