--- a/include/o3tl/lru_map.hxx	2021-01-23 22:37:48.903253658 +1100
+++ b/include/o3tl/lru_map.hxx	2021-01-23 07:08:51.192264951 +1100
@@ -48,7 +48,7 @@
 
     list_t mLruList;
     map_t mLruMap;
-    const size_t mMaxSize;
+    const std::size_t mMaxSize;
 
     void checkLRU()
     {
@@ -66,7 +66,7 @@
     typedef list_const_iterator_t const_iterator;
 
     // a size of 0 effectively disables the LRU cleanup code
-    lru_map(size_t nMaxSize)
+    lru_map(std::size_t nMaxSize)
         : mMaxSize(nMaxSize ? nMaxSize : std::min(mLruMap.max_size(), mLruList.max_size()))
     {}
     ~lru_map()
@@ -165,7 +165,7 @@
         return mLruList.cend();
     }
 
-    size_t size() const
+    std::size_t size() const
     {
         assert(mLruMap.size() == mLruList.size());
         return mLruMap.size();