diff --git a/include/hwbinder/ProcessState.h b/include/hwbinder/ProcessState.h
index 2f72059..8a9e47a 100644
--- a/include/hwbinder/ProcessState.h
+++ b/include/hwbinder/ProcessState.h
@@ -117,7 +117,7 @@
             bool                mThreadPoolStarted;
             bool                mSpawnThreadOnStart;
     volatile int32_t            mThreadPoolSeq;
-            size_t              mMmapSize;
+            const size_t        mMmapSize;
 };
 
 }; // namespace hardware