diff --git a/scripts/tests/xmas.lua b/scripts/tests/xmas.lua
index 7ac4ce731..5477e08ab 100644
--- a/scripts/tests/xmas.lua
+++ b/scripts/tests/xmas.lua
@@ -8,6 +8,8 @@ function setup()
     eressea.settings.set("rules.grow.formula", "0")
     eressea.settings.set("rules.peasants.growth.factor", "0")
     eressea.settings.set("volcano.active.percent", "0")
+    eressea.settings.set("volcano.outbreak.percent", "0")
+    eressea.settings.set("volcano.stop.percent", "0")
 end
 
 function test_snowglobe_fail()
diff --git a/src/volcano.c b/src/volcano.c
index a9a4f0ba7..89a865017 100644
--- a/src/volcano.c
+++ b/src/volcano.c
@@ -256,11 +256,19 @@ void volcano_outbreak(region * r, region *rn)
 }
 
 static bool stop_smoke_chance(void) {
-    return rng_int() % 100 < 12;
+    static int cache, percent = 0;
+    if (config_changed(&cache)) {
+        percent = config_get_int("volcano.stop.percent", 12);
+    }
+    return percent!=0 && (rng_int() % 100) < percent;
 }
 
 static bool outbreak_chance(void) {
-    return rng_int() % 100 < 8;
+    static int cache, percent = 0;
+    if (config_changed(&cache)) {
+        percent = config_get_int("volcano.outbreak.percent", 8);
+    }
+    return percent!=0 && (rng_int() % 100) < percent;
 }
 
 void volcano_update(void)