diff --git a/src/addrman.h b/src/addrman.h
index cde9430ae..2a08076b7 100644
--- a/src/addrman.h
+++ b/src/addrman.h
@@ -470,7 +470,7 @@ public:
     }
 
     //! Return the number of (unique) addresses in all tables.
-    int size()
+    size_t size() const
     {
         return vRandom.size();
     }