diff --git a/gtk/gtkgridview.c b/gtk/gtkgridview.c
index 2d91fd5096..93ae91cee2 100644
--- a/gtk/gtkgridview.c
+++ b/gtk/gtkgridview.c
@@ -627,6 +627,8 @@ gtk_grid_view_compute_n_columns (GtkGridView *self,
 
   n_columns = CLAMP (n_columns, self->min_columns, self->max_columns);
 
+  g_assert (n_columns > 0);
+
   return n_columns;
 }
 
@@ -869,6 +871,8 @@ gtk_grid_view_size_allocate (GtkWidget *widget,
   i = 0;
   row_height = 0;
 
+  g_assert (self->n_columns > 0);
+
   for (cell = gtk_list_item_manager_get_first (self->item_manager);
        cell != NULL;
        cell = gtk_rb_tree_node_get_next (cell))