diff --git a/retroshare-gui/src/gui/Posted/PostedItem.h b/retroshare-gui/src/gui/Posted/PostedItem.h
index 2f1bc51b1..a679efd0d 100644
--- a/retroshare-gui/src/gui/Posted/PostedItem.h
+++ b/retroshare-gui/src/gui/Posted/PostedItem.h
@@ -123,6 +123,13 @@ private:
 	Ui::PostedItem *ui;
 };
 
+// Qt5 only (see GxsFeedItem.h/GxsGroupFeedItem.h): Qt6 auto-registers this
+// complete type with the metatype system, and an explicit specialization here
+// clashes with the implicit QMetaTypeId instantiation in CMake AUTOMOC's single
+// mocs_compilation.cpp translation unit ("specialization after instantiation").
+// qmake compiles each moc separately.
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
 Q_DECLARE_METATYPE(RsPostedPost)
+#endif
 
 #endif
diff --git a/retroshare-gui/src/gui/Posted/PostedListWidgetWithModel.cpp b/retroshare-gui/src/gui/Posted/PostedListWidgetWithModel.cpp
index e39c4aeed..4dcaed2fb 100644
--- a/retroshare-gui/src/gui/Posted/PostedListWidgetWithModel.cpp
+++ b/retroshare-gui/src/gui/Posted/PostedListWidgetWithModel.cpp
@@ -77,8 +77,6 @@ static const int POSTED_TABS_POSTS  = 1;
 #define IMAGE_AUTHOR       ":/images/user/personal64.png"
 #define IMAGE_COPYHTTP     ":/images/emblem-web.png"
 
-Q_DECLARE_METATYPE(RsPostedPost);
-
 // Delegate used to paint into the table of thumbnails
 
 //===================================================================================================================================
diff --git a/retroshare-gui/src/gui/Posted/PostedPostsModel.cpp b/retroshare-gui/src/gui/Posted/PostedPostsModel.cpp
index cb42c3c73..2461e61e1 100644
--- a/retroshare-gui/src/gui/Posted/PostedPostsModel.cpp
+++ b/retroshare-gui/src/gui/Posted/PostedPostsModel.cpp
@@ -36,7 +36,6 @@
 //#define DEBUG_CHANNEL_MODEL
 
 Q_DECLARE_METATYPE(RsMsgMetaData)
-Q_DECLARE_METATYPE(RsPostedPost)
 
 const uint32_t RsPostedPostsModel::DEFAULT_DISPLAYED_NB_POSTS = 10;