diff --git a/xo-alloc/include/xo/alloc/GC.hpp b/xo-alloc/include/xo/alloc/GC.hpp
index d145e2c7..313306bc 100644
--- a/xo-alloc/include/xo/alloc/GC.hpp
+++ b/xo-alloc/include/xo/alloc/GC.hpp
@@ -119,6 +119,8 @@ namespace xo {
          **/
         class GcCopyCallback {
         public:
+            virtual ~GcCopyCallback() = default;
+
             virtual void notify_gc_copy(std::size_t z, const void * src_addr, const void * dest_addr,
                                         generation src_gen, generation dest_gen) = 0;
             /** invoked when added to callback set (i.e. @ref GC::GcCopyCallbackSet) **/
diff --git a/xo-alloc/include/xo/alloc/ObjectStatistics.hpp b/xo-alloc/include/xo/alloc/ObjectStatistics.hpp
index ced3b463..43ddd70e 100644
--- a/xo-alloc/include/xo/alloc/ObjectStatistics.hpp
+++ b/xo-alloc/include/xo/alloc/ObjectStatistics.hpp
@@ -56,7 +56,8 @@ namespace xo {
          *
          *  Passed to @ref Object::deep_move for example
          **/
-        struct ObjectStatistics {
+        class ObjectStatistics {
+        public:
             void display(std::ostream & os) const;
 
             /** per-object-type statistics, indexed by TypeId **/
diff --git a/xo-alloc/src/alloc/ArenaAlloc.cpp b/xo-alloc/src/alloc/ArenaAlloc.cpp
index 9703d103..4fdcefe8 100644
--- a/xo-alloc/src/alloc/ArenaAlloc.cpp
+++ b/xo-alloc/src/alloc/ArenaAlloc.cpp
@@ -9,6 +9,7 @@
 #include "xo/indentlog/scope.hpp"
 #include "xo/indentlog/print/tag.hpp"
 #include <sys/mman.h>
+#include <unistd.h> // for getpagesize() on OSX
 #include <cassert>
 
 namespace xo {
diff --git a/xo-unit/include/xo/unit/quantity.hpp b/xo-unit/include/xo/unit/quantity.hpp
index 0760d428..178cf2e9 100644
--- a/xo-unit/include/xo/unit/quantity.hpp
+++ b/xo-unit/include/xo/unit/quantity.hpp
@@ -508,7 +508,7 @@ namespace xo {
                   && Q1::always_constexpr_unit
                   && Q2::always_constexpr_unit)
         constexpr auto
-        with_units_from(const Q1 & x, const Q2 & y)
+        with_units_from(const Q1 & x, const Q2 & /*y*/)
         {
             return x.template rescale_ext<Unit>();
         }