diff --git a/src/volcano.c b/src/volcano.c
index 7df53b62c..9649efa5b 100644
--- a/src/volcano.c
+++ b/src/volcano.c
@@ -119,8 +119,9 @@ int volcano_damage(unit* u, const char* dice)
             }
         }
     }
+    total = u->hp - total;
     scale_number(u, u->number - dead);
-    u->hp -= total;
+    u->hp = total;
     return dead;
 }
 
diff --git a/src/volcano.test.c b/src/volcano.test.c
index 358dccd02..7fe8f653d 100644
--- a/src/volcano.test.c
+++ b/src/volcano.test.c
@@ -47,6 +47,8 @@ static void test_volcano_damage(CuTest* tc) {
     u = test_create_unit(test_create_faction(), test_create_plain(0, 0));
     scale_number(u, 100);
     u->hp = u->number * 20;
+    CuAssertIntEquals(tc, 0, volcano_damage(u, "0"));
+    CuAssertIntEquals(tc, u->number * 20, u->hp);
     CuAssertIntEquals(tc, 0, volcano_damage(u, "10"));
     CuAssertIntEquals(tc, u->number * 10, u->hp);
     CuAssertIntEquals(tc, 0, volcano_damage(u, "d9"));