diff --git a/scripts/tests/eressea.lua b/scripts/tests/eressea.lua
index f33726886..87a493e5e 100644
--- a/scripts/tests/eressea.lua
+++ b/scripts/tests/eressea.lua
@@ -2,6 +2,23 @@ require "lunit"
 
 module("tests.e3.e2features", package.seeall, lunit.testcase )
 
+local function one_unit(r, f)
+  local u = unit.create(f, r, 1)
+  u:add_item("money", u.number * 100)
+  u:clear_orders()
+  return u
+end
+
+local function two_factions()
+  local f1 = faction.create("one@eressea.de", "human", "de")
+  local f2 = faction.create("two@eressea.de", "human", "de")
+  return f1, f2
+end
+
+local function two_units(r, f1, f2)
+  return one_unit(r, f1), one_unit(r, f2)
+end
+
 function setup()
     eressea.free_game()
     eressea.settings.set("nmr.timeout", "0")
@@ -200,3 +217,92 @@ function test_snowman()
     end
     assert_equal(nil, u)
 end
+
+function test_block_movement()
+  eressea.settings.set("rules.guard.base_stop_prob", "0.3")
+  eressea.settings.set("rules.guard.amulet_stop_prob", "0.0")
+  eressea.settings.set("rules.guard.skill_stop_prob", "0.1")
+
+  local r0 = region.create(0, 0, "plain")
+  local r1 = region.create(1, 0, "plain")
+  local r2 = region.create(2, 0, "plain")
+  local f1, f2 = two_factions()
+  f1.age=20
+  f2.age=20
+
+  local u11 = one_unit(r1, f1)
+  local u2 = { }
+  for i = 1, 20 do
+    u2[i] = one_unit(r0, f2)
+  end
+  
+  u11:add_item("sword", 1)
+  u11:add_item("money", 1)
+  u11:set_skill("melee", 1)
+  u11:set_skill("perception", 7)
+  u11:clear_orders()
+  u11:add_order("BEWACHEN")
+  
+  process_orders()
+  
+  for i, u in ipairs(u2) do
+    u:add_item("horse", 1)
+  	u:set_skill("riding", 1)
+  	u:clear_orders()
+  	u:add_order("NACH o o")
+  end
+  
+  u2[1]:set_skill("stealth", 8)
+  
+  process_orders()
+
+  assert_equal(r2, u2[1].region, "nobody should see me")
+  for i, u in ipairs(u2) do
+    if i > 1 then
+      assert_equal(r1, u.region, "perception +7 should always stop me")
+    end
+  end
+end
+
+
+
+function test_block_movement_aots()
+  eressea.settings.set("rules.guard.base_stop_prob", "0.0")
+  eressea.settings.set("rules.guard.skill_stop_prob", "1.0")
+  eressea.settings.set("rules.guard.amulet_stop_prob", "1.1")
+
+  local r0 = region.create(0, 0, "plain")
+  local r1 = region.create(1, 0, "plain")
+  local r2 = region.create(2, 0, "plain")
+  local f1, f2 = two_factions()
+  f1.age=20
+  f2.age=20
+
+  local u11, u12 = two_units(r1, f1, f1)
+  local u21, u22 = two_units(r0, f2, f2)
+  
+  for i, u in ipairs ({ u11, u12 }) do
+    u:add_item("sword", 1)
+  	u:add_item("money", 1)
+  	u:set_skill("melee", 1)
+  	u:clear_orders()
+  	u:add_order("BEWACHEN")
+  end
+  
+  process_orders()
+  
+  for i, u in ipairs ({ u21, u22 }) do
+    u:add_item("horse", 1)
+  	u:set_skill("riding", 1)
+  	u:clear_orders()
+  	u:add_order("NACH o o")
+  end
+  
+  u12:add_item("aots", 10)
+  u22:set_skill("stealth", 1)
+
+  process_orders()
+
+  assert_equal(r1, u21.region, "unit with amulet should stop me")
+  assert_equal(r2, u22.region, "nobody should see me")
+end
diff --git a/src/kernel/move.c b/src/kernel/move.c
index fb975adb8..49e35073b 100644
--- a/src/kernel/move.c
+++ b/src/kernel/move.c
@@ -828,9 +828,24 @@ static void caught_target(region * r, unit * u)
 static unit *bewegung_blockiert_von(unit * reisender, region * r)
 {
   unit *u;
-  int perception = 0;
+  double prob = 0.0;
   bool contact = false;
   unit *guard = NULL;
+  int stealth = eff_stealth(reisender, r);
+  static int gamecookie = -1;
+  static double base_prob = -999;
+  static double skill_prob = -999;
+  static double amulet_prob = -999;
+
+  if (gamecookie < 0 || gamecookie != global.cookie) {
+    base_prob =
+      get_param_flt(global.parameters, "rules.guard.base_stop_prob", .3);
+    skill_prob =
+      get_param_flt(global.parameters, "rules.guard.skill_stop_prob", .1);
+    amulet_prob =
+      get_param_flt(global.parameters, "rules.guard.amulet_stop_prob", .1);
+    gamecookie = global.cookie;
+  }
 
   if (fval(u_race(reisender), RCF_ILLUSIONARY))
     return NULL;
@@ -845,16 +860,19 @@ static unit *bewegung_blockiert_von(unit * reisender, region * r)
         contact = true;
       else if (alliedunit(u, reisender->faction, HELP_GUARD))
         contact = true;
-      else if (sk >= perception) {
-        perception = sk;
-        guard = u;
+      else if (sk >= stealth) {
+    	  double prob_u = (sk - stealth) * skill_prob;
+    	  /* amulet counts at most once */
+    	  prob_u += _min (1, _min(u->number, get_item(u, I_AMULET_OF_TRUE_SEEING))) * amulet_prob;
+    	  if (prob_u >= prob) {
+    		  prob = prob_u;
+    		  guard = u;
+    	  }
       }
     }
   }
   if (!contact && guard) {
-    double prob = 0.3;          /* 30% base chance */
-    prob += 0.1 * (perception - eff_stealth(reisender, r));
-    prob += 0.1 * _min(guard->number, get_item(guard, I_AMULET_OF_TRUE_SEEING));
+    prob += base_prob;          /* 30% base chance */
 
     if (chance(prob)) {
       return guard;