diff --git a/src/apprt/gtk-ng/class/split_tree.zig b/src/apprt/gtk-ng/class/split_tree.zig
index 3ee36f646..10815bb0a 100644
--- a/src/apprt/gtk-ng/class/split_tree.zig
+++ b/src/apprt/gtk-ng/class/split_tree.zig
@@ -909,6 +909,7 @@ pub const SplitTree = extern struct {
             gobject.ext.registerProperties(class, &.{
                 properties.@"active-surface".impl,
                 properties.@"has-surfaces".impl,
+                properties.@"is-zoomed".impl,
                 properties.tree.impl,
             });