diff --git a/src/ui_signals.cpp b/src/ui_signals.cpp
index 32f9e05..86e10d5 100644
--- a/src/ui_signals.cpp
+++ b/src/ui_signals.cpp
@@ -189,10 +189,22 @@ GtkWidget* make_math_divider(App& app) {
   return row;
 }
 
+/// A handler that rebuilds the signal list destroys the widget it was emitted from -- the row it
+/// lives in, and that row's menu popover with it. GLib holds a reference for the duration of *one*
+/// emission, and a button's own code keeps running after the handler returns, so the last reference
+/// has to outlive the emission: hold one here and drop it from an idle. This is the same repair
+/// `on_signal_switch()` makes, for the same reason.
+static void outlive_the_rebuild(GtkWidget* widget) {
+  g_object_ref(widget);
+  g_idle_add_full(G_PRIORITY_DEFAULT_IDLE,
+                  +[](gpointer) -> gboolean { return G_SOURCE_REMOVE; }, widget, g_object_unref);
+}
+
 /// Create a channel, then open the editor on it: a new channel is a single `Source` node with a
 /// default name, which is of no use until it is given a graph.
-void on_math_add_clicked(GtkButton*, gpointer user) {
+void on_math_add_clicked(GtkButton* button, gpointer user) {
   App* a = static_cast<App*>(user);
+  outlive_the_rebuild(GTK_WIDGET(button));
   add_math_channel(*a);
   if (a->math.empty()) return;
   // `add_math_channel()` appended, so the new channel is the last one; `apply_math_channels()`
@@ -233,6 +245,7 @@ void on_math_delete_clicked(GtkButton* button, gpointer user) {
   const int k = math_index_for_signal(*a, signal_name_at(*a, index));
   if (k < 0) return;
   dismiss_row_menu(button);
+  outlive_the_rebuild(GTK_WIDGET(button));
   a->math.erase(a->math.begin() + k);
   // Rebuilds the model's signal list, the plots and this list, and schedules the save.
   apply_math_channels(*a);