diff --git a/data/helpers.d/filesystem b/data/helpers.d/filesystem
index 6fb073e06..6f24a7777 100644
--- a/data/helpers.d/filesystem
+++ b/data/helpers.d/filesystem
@@ -47,6 +47,12 @@ ynh_backup() {
     local DEST_PATH="${2:-}"
     local IS_BIG="${3:-0}"
 
+    # If backing up core only (used by ynh_backup_before_upgrade),
+    # don't backup big data items
+    if [ "$IS_BIG" == "1" ] && [ -n "$BACKUP_CORE_ONLY" ] ; then
+      return 0
+    fi
+    
     # ==============================================================================
     # Format correctly source and destination paths
     # ==============================================================================