diff --git a/config.cpp b/config.cpp
index dab1ab99..cb987c1b 100644
--- a/config.cpp
+++ b/config.cpp
@@ -906,6 +906,8 @@ EX void initConfig() {
   
   addsaver(viewdists, "expansion mode");
   param_f(backbrightness, "back", "brightness behind sphere");
+  param_b(auto_extend, "expansion_auto_extend")
+  -> editable("extend automatically", 'E');
 
   param_f(vid.ipd, "ipd", "interpupilar-distance", 0.05);
   param_f(vid.lr_eyewidth, "lr", "eyewidth-lr", 0.5);
diff --git a/expansion.cpp b/expansion.cpp
index 21cb98a2..1f156075 100644
--- a/expansion.cpp
+++ b/expansion.cpp
@@ -702,6 +702,8 @@ string produce_coef_formula(vector<int> coef) {
   return fmt;
   }
 
+EX bool auto_extend = true;
+
 void expansion_analyzer::view_distances_dialog() {
   static int lastticks;
   if(scrolling_distances && !closed_manifold) {
@@ -788,10 +790,13 @@ void expansion_analyzer::view_distances_dialog() {
     scrolling_distances = false;
     dialog::editNumber(last_distance, 0, 3000, 1, 0, XLAT("display distances up to"), "");
     dialog::bound_low(0);
+    dialog::extra_options = [] {
+      add_edit(auto_extend);
+      };
     });
 
   dialog::display();
-  if(dialog::list_skip + dialog::list_actual_size == dialog::list_full_size) last_distance++;
+  if(auto_extend && dialog::list_skip + dialog::list_actual_size == dialog::list_full_size) last_distance++;
   }
 
 EX void enable_viewdists() {