diff --git a/xo-gc/idl/GCObject.json5 b/xo-gc/idl/GCObject.json5
index 7056f0b8..43747582 100644
--- a/xo-gc/idl/GCObject.json5
+++ b/xo-gc/idl/GCObject.json5
@@ -14,7 +14,7 @@
     namespace1: "xo",
     namespace2: "mm",
     pretext: [
-        "namespace xo { namespace mm { struct ACollector; }}",
+        "namespace xo { namespace mm { class ACollector; }}",
     ],
     facet: "GCObject",
     detail_subdir: "detail",
diff --git a/xo-gc/include/xo/gc/detail/ACollector.hpp b/xo-gc/include/xo/gc/detail/ACollector.hpp
index 0fd031fb..bd19fe51 100644
--- a/xo-gc/include/xo/gc/detail/ACollector.hpp
+++ b/xo-gc/include/xo/gc/detail/ACollector.hpp
@@ -30,7 +30,8 @@ namespace xo {
          *
          *  A collector implementation will also support the @ref AAllocator facet, see also
          **/
-        struct ACollector {
+        class ACollector {
+        public:
             using typeseq = xo::facet::typeseq;
             using size_type = std::size_t;
 
diff --git a/xo-gc/include/xo/gc/detail/AGCObject.hpp b/xo-gc/include/xo/gc/detail/AGCObject.hpp
index 98f7e258..6f6e7b92 100644
--- a/xo-gc/include/xo/gc/detail/AGCObject.hpp
+++ b/xo-gc/include/xo/gc/detail/AGCObject.hpp
@@ -22,7 +22,7 @@
 #include <xo/facet/facet_implementation.hpp>
 #include <xo/facet/typeseq.hpp>
 
-namespace xo { namespace mm { struct ACollector; }}
+namespace xo { namespace mm { class ACollector; }}
 
 namespace xo {
 namespace mm {