diff --git a/src/bindings/bind_unit.c b/src/bindings/bind_unit.c
index 139740237..3b0198d2c 100644
--- a/src/bindings/bind_unit.c
+++ b/src/bindings/bind_unit.c
@@ -614,20 +614,20 @@ static int tolua_unit_get_building(lua_State * L)
   return 1;
 }
 
-static void unit_setbuilding(unit * u, building * b)
-{
-  leave(u, true);
-  if (b && u->region != b->region) {
-    move_unit(u, b->region, NULL);
-  }
-  u->building = b;
-}
-
 static int tolua_unit_set_building(lua_State * L)
 {
-  unit *self = (unit *) tolua_tousertype(L, 1, 0);
-  if (self->faction) {
-    unit_setbuilding(self, (building *) tolua_tousertype(L, 2, 0));
+  unit *u = (unit *) tolua_tousertype(L, 1, 0);
+  if (u->faction) {
+    building * b = (building *) tolua_tousertype(L, 2, 0);
+    if (b!=u->building) {
+      leave(u, true);
+      if (b) {
+        if (u->region != b->region) {
+          move_unit(u, b->region, NULL);
+        }
+        u_set_building(u, b);
+      }
+    }
   }
   return 0;
 }
diff --git a/src/gamecode/economy.c b/src/gamecode/economy.c
index 32c7e1182..6b99573a8 100644
--- a/src/gamecode/economy.c
+++ b/src/gamecode/economy.c
@@ -639,10 +639,8 @@ static void give_control(unit * u, unit * u2)
     }
   }
   if (u->ship) {
-    u->ship->owner = u2;
+    ship_set_owner(u->ship, u2);
   }
-  freset(u, UFL_OWNER);
-  fset(u2, UFL_OWNER);
 }
 
 int give_control_cmd(unit * u, order * ord)
diff --git a/src/gamecode/laws_test.c b/src/gamecode/laws_test.c
index 02af945dc..e8fbd1895 100644
--- a/src/gamecode/laws_test.c
+++ b/src/gamecode/laws_test.c
@@ -53,7 +53,7 @@ static void test_rename_building(CuTest * tc)
   b = new_building(btype, r, default_locale);
   f = test_create_faction(rc_find("human"));
   u = test_create_unit(f, r);
-  u->building = b;
+  u_set_building(u, b);
   fset(u, UFL_OWNER);
 
   rename_building(u, NULL, b, "Villa Nagel");
@@ -77,8 +77,7 @@ static void test_rename_building_twice(CuTest * tc)
   b = new_building(btype, r, default_locale);
   f = test_create_faction(rc_find("human"));
   u = test_create_unit(f, r);
-  u->building = b;
-  fset(u, UFL_OWNER);
+  u_set_building(u, b);
 
   rename_building(u, NULL, b, "Villa Nagel");
   CuAssertStrEquals(tc, "Villa Nagel", b->name);
diff --git a/src/gamecode/market_test.c b/src/gamecode/market_test.c
index d60c71982..c60876995 100644
--- a/src/gamecode/market_test.c
+++ b/src/gamecode/market_test.c
@@ -61,8 +61,7 @@ static void market_curse(CuTest * tc)
 
   f = addfaction("nobody@eressea.de", NULL, rc, default_locale, 0);
   u = create_unit(r, f, 1, f->race, 0, 0, 0);
-  u->building = b;
-  u->flags |= UFL_OWNER;
+  u_set_building(u, b);
 
   do_markets();
 
diff --git a/src/gamecode/randenc.c b/src/gamecode/randenc.c
index a84f792b5..b0f422f0b 100644
--- a/src/gamecode/randenc.c
+++ b/src/gamecode/randenc.c
@@ -911,8 +911,9 @@ static void move_iceberg(region * r)
       while (rc->units) {
         building *b = rc->units->building;
         u = rc->units;
+        u->building = 0; /* prevent leaving in move_unit */
         move_unit(rc->units, r, NULL);
-        u->building = b;        /* move_unit macht ein leave() */
+        u_set_building(u, b); /* undo leave-prevention */
       }
 
       /* Beschädigte Schiffe können sinken */
diff --git a/src/kernel.vcxproj b/src/kernel.vcxproj
index c998520ac..240cc1a6d 100644
--- a/src/kernel.vcxproj
+++ b/src/kernel.vcxproj
@@ -94,6 +94,7 @@
     <ClCompile Include="kernel\binarystore.c" />
     <ClCompile Include="kernel\build.c" />
     <ClCompile Include="kernel\building.c" />
+    <ClCompile Include="kernel\building_test.c" />
     <ClCompile Include="kernel\calendar.c" />
     <ClCompile Include="kernel\command.c" />
     <ClCompile Include="kernel\config.c" />
diff --git a/src/kernel.vcxproj.filters b/src/kernel.vcxproj.filters
index 0239a0193..8c6cdcdf1 100644
--- a/src/kernel.vcxproj.filters
+++ b/src/kernel.vcxproj.filters
@@ -304,6 +304,9 @@
     <ClCompile Include="kernel\reports_test.c">
       <Filter>kernel</Filter>
     </ClCompile>
+    <ClCompile Include="kernel\building_test.c">
+      <Filter>kernel</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="kernel\alchemy.h">
diff --git a/src/kernel/battle_test.c b/src/kernel/battle_test.c
index ceac668c7..c86a7f0b8 100644
--- a/src/kernel/battle_test.c
+++ b/src/kernel/battle_test.c
@@ -77,7 +77,7 @@ static void test_defenders_get_building_bonus(CuTest * tc)
 
   du = test_create_unit(test_create_faction(rc_find("human")), r);
   au = test_create_unit(test_create_faction(rc_find("human")), r);
-  du->building = bld;
+  u_set_building(du, bld);
 
   b = make_battle(r);
   ds = make_side(b, du->faction, 0, 0, 0);
@@ -119,8 +119,7 @@ static void test_attackers_get_no_building_bonus(CuTest * tc)
   bld->size = 10;
 
   au = test_create_unit(test_create_faction(rc_find("human")), r);
-  au->building = bld;
-
+  u_set_building(au, bld);
 
   b = make_battle(r);
   as = make_side(b, au->faction, 0, 0, 0);
@@ -151,9 +150,9 @@ static void test_building_bonus_respects_size(CuTest * tc)
   f = test_create_faction(rc_find("human"));
   au = test_create_unit(f, r);
   scale_number(au, 9);
-  au->building = bld;
+  u_set_building(au, bld);
   du = test_create_unit(f, r);
-  du->building = bld;
+  u_set_building(du, bld);
   scale_number(du, 2);
 
   b = make_battle(r);
diff --git a/src/kernel/build.c b/src/kernel/build.c
index a3ab10b8c..fcda6483f 100644
--- a/src/kernel/build.c
+++ b/src/kernel/build.c
@@ -360,14 +360,13 @@ int destroy_cmd(unit * u, struct order *ord)
     return 0;
   }
 
-  if (!fval(u, UFL_OWNER)) {
-    cmistake(u, ord, 138, MSG_PRODUCE);
-    return 0;
-  }
-
   if (u->building) {
     building *b = u->building;
 
+    if (u!=building_owner(b)) {
+      cmistake(u, ord, 138, MSG_PRODUCE);
+      return 0;
+    }
     if (fval(b->type, BTF_INDESTRUCTIBLE)) {
       cmistake(u, ord, 138, MSG_PRODUCE);
       return 0;
@@ -377,8 +376,8 @@ int destroy_cmd(unit * u, struct order *ord)
       /* all units leave the building */
       for (u2 = r->units; u2; u2 = u2->next) {
         if (u2->building == b) {
-          u2->building = 0;
           freset(u2, UFL_OWNER);
+          leave_building(u2);
         }
       }
       ADDMSG(&u->faction->msgs, msg_message("destroy", "building unit", b, u));
@@ -393,6 +392,10 @@ int destroy_cmd(unit * u, struct order *ord)
   } else if (u->ship) {
     sh = u->ship;
 
+    if (u!=ship_owner(sh)) {
+      cmistake(u, ord, 138, MSG_PRODUCE);
+      return 0;
+    }
     if (fval(r->terrain, SEA_REGION)) {
       cmistake(u, ord, 14, MSG_EVENT);
       return 0;
@@ -970,8 +973,8 @@ build_building(unit * u, const building_type * btype, int want, order * ord)
 
     /* Die Einheit befindet sich automatisch im Inneren der neuen Burg. */
     if (leave(u, false)) {
-      u->building = b;
-      fset(u, UFL_OWNER);
+      u_set_building(u, b);
+      assert(building_owner(b)==u);
     }
 #ifdef WDW_PYRAMID
     if (b->type == bt_find("pyramid") && f_get_alliance(u->faction) != NULL) {
@@ -1297,11 +1300,8 @@ static boolean enter_building(unit * u, order * ord, int id, boolean report)
   }
 
   if (leave(u, false)) {
-    if (building_owner(b) == 0) {
-      fset(u, UFL_OWNER);
-    }
     fset(u, UFL_ENTER);
-    u->building = b;
+    u_set_building(u, b);
     return true;
   }
   return false;
diff --git a/src/kernel/building.c b/src/kernel/building.c
index f36636047..1295d47b1 100644
--- a/src/kernel/building.c
+++ b/src/kernel/building.c
@@ -145,8 +145,9 @@ building_type *bt_find(const char *name)
 
 void bt_register(building_type * type)
 {
-  if (type->init)
+  if (type->init) {
     type->init(type);
+  }
   ql_push(&buildingtypes, (void *)type);
 }
 
@@ -616,43 +617,44 @@ const char *buildingname(const building * b)
 
 void building_set_owner(struct building *b, struct unit * owner)
 {
-  unit * u;
-
   assert(b && owner && owner->building==b);
-
-  for (u = b->region->units; u; u = u->next) {
-    if (u->building == b) {
-      freset(owner, UFL_OWNER);
-    }
+  if (b->_owner && b->_owner!=owner) {
+    freset(b->_owner, UFL_OWNER);
   }
+  b->_owner = owner;
   fset(owner, UFL_OWNER);
 }
 
-unit *building_owner(const building * b)
+unit *building_owner(const building * bld)
 {
-  unit *u = NULL;
-  unit *first = NULL;
-  region *r = b->region;
-  /* Prüfen ob Eigentümer am leben. */
+  unit *owner = bld->_owner;
+  if (owner && (owner->building!=bld || owner->number<=0)) {
+    unit *u, *heir = 0;
 
-  for (u = r->units; u; u = u->next) {
-    if (u->building == b) {
-      if (!first && u->number > 0)
-        first = u;
-      if (fval(u, UFL_OWNER) && u->number > 0)
-        return u;
-      if (u->number == 0)
+    /* Eigentümer tot oder kein Eigentümer vorhanden. Erste lebende Einheit
+     * nehmen. */
+    for (u = bld->region->units; u; u = u->next) {
+      if (u->building == bld) {
+        if (u->number > 0) {
+          if (u->faction==owner->faction) {
+            heir = u;
+            break;
+          }
+          else if (!heir) {
+            heir = u; /* you'll do in an emergency */
+          }
+        }
         freset(u, UFL_OWNER);
+      }
+    }
+    freset(owner, UFL_OWNER);
+    owner->building = 0;
+    owner = heir;
+    if (owner) {
+      fset(owner, UFL_OWNER);
     }
   }
-
-  /* Eigentümer tot oder kein Eigentümer vorhanden. Erste lebende Einheit
-   * nehmen. */
-
-  if (first) {
-    fset(first, UFL_OWNER);
-  }
-  return first;
+  return owner;
 }
 
 const char *building_getname(const building * self)
diff --git a/src/kernel/building.h b/src/kernel/building.h
index 7fdbfaf1e..bacf91d93 100644
--- a/src/kernel/building.h
+++ b/src/kernel/building.h
@@ -104,6 +104,7 @@ extern "C" {
 
     const struct building_type *type;
     struct region *region;
+    struct unit *_owner; /* you should always use building_owner(), never this naked pointer */
     char *name;
     char *display;
     struct attrib *attribs;
diff --git a/src/kernel/building_test.c b/src/kernel/building_test.c
new file mode 100644
index 000000000..0e09aa1c8
--- /dev/null
+++ b/src/kernel/building_test.c
@@ -0,0 +1,324 @@
+#include <platform.h>
+
+#include <kernel/config.h>
+#include <kernel/types.h>
+#include <kernel/race.h>
+#include <kernel/region.h>
+#include <kernel/building.h>
+#include <kernel/unit.h>
+
+#include <cutest/CuTest.h>
+#include <tests.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void test_register_building(CuTest * tc)
+{
+  building_type *btype;
+
+  test_cleanup();
+
+  btype = (building_type *)calloc(sizeof(building_type), 1);
+  btype->_name = strdup("herp");
+  bt_register(btype);
+
+  CuAssertPtrNotNull(tc, bt_find("herp"));
+}
+
+static void test_building_set_owner(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u1, *u2;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  btype = bt_find("castle");
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  u1 = test_create_unit(f, r);
+  u_set_building(u1, bld);
+  CuAssertPtrEquals(tc, u1, building_owner(bld));
+
+  u2 = test_create_unit(f, r);
+  u_set_building(u2, bld);
+  CuAssertPtrEquals(tc, u1, building_owner(bld));
+  building_set_owner(bld, u2);
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+}
+
+static void test_buildingowner_goes_to_next_after_death(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u = test_create_unit(f, r);
+  u2 = test_create_unit(f, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  u_set_building(u2, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  u->number = 0;
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+}
+
+static void test_buildingowner_goes_to_other_after_death(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u2 = test_create_unit(f, r);
+  u = test_create_unit(f, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  u_set_building(u2, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  u->number = 0;
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+}
+
+static void test_buildingowner_goes_to_same_faction_after_death(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2, *u3;
+  struct faction *f1, *f2;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f1 = test_create_faction(human);
+  f2 = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u2 = test_create_unit(f2, r);
+  u3 = test_create_unit(f1, r);
+  u = test_create_unit(f1, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  u_set_building(u2, bld);
+  u_set_building(u3, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  CuAssertTrue(tc, fval(u, UFL_OWNER));
+  u->number = 0;
+  CuAssertPtrEquals(tc, u3, building_owner(bld));
+  CuAssertTrue(tc, !fval(u, UFL_OWNER));
+  CuAssertTrue(tc, fval(u3, UFL_OWNER));
+  u3->number = 0;
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+  CuAssertTrue(tc, !fval(u3, UFL_OWNER));
+  CuAssertTrue(tc, fval(u2, UFL_OWNER));
+}
+
+static void test_buildingowner_goes_to_next_after_leave(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u = test_create_unit(f, r);
+  u2 = test_create_unit(f, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  u_set_building(u2, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  leave_building(u);
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+}
+
+static void test_buildingowner_goes_to_other_after_leave(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u2 = test_create_unit(f, r);
+  u = test_create_unit(f, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  u_set_building(u2, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  leave_building(u);
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+}
+
+static void test_buildingowner_goes_to_same_faction_after_leave(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u, *u2, *u3;
+  struct faction *f1, *f2;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f1 = test_create_faction(human);
+  f2 = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u2 = test_create_unit(f2, r);
+  u3 = test_create_unit(f1, r);
+  u = test_create_unit(f1, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  u_set_building(u2, bld);
+  u_set_building(u3, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  leave_building(u);
+  CuAssertPtrEquals(tc, u3, building_owner(bld));
+  leave_building(u3);
+  CuAssertPtrEquals(tc, u2, building_owner(bld));
+  leave_building(u2);
+  CuAssertPtrEquals(tc, 0, building_owner(bld));
+}
+
+static void test_buildingowner_resets_when_dead(CuTest * tc)
+{
+  struct region *r;
+  struct building *bld;
+  struct unit *u;
+  struct faction *f;
+  const struct building_type *btype;
+  const struct race *human;
+
+  test_cleanup();
+  test_create_world();
+
+  human = rc_find("human");
+  CuAssertPtrNotNull(tc, human);
+
+  btype = bt_find("castle");
+  CuAssertPtrNotNull(tc, btype);
+
+  f = test_create_faction(human);
+  r = findregion(0, 0);
+
+  bld = test_create_building(r, btype);
+  CuAssertPtrNotNull(tc, bld);
+
+  u = test_create_unit(f, r);
+  CuAssertPtrNotNull(tc, u);
+  u_set_building(u, bld);
+  CuAssertPtrEquals(tc, u, building_owner(bld));
+  u->number = 0;
+  CuAssertPtrEquals(tc, 0, building_owner(bld));
+}
+
+CuSuite *get_building_suite(void)
+{
+  CuSuite *suite = CuSuiteNew();
+  SUITE_ADD_TEST(suite, test_register_building);
+  SUITE_ADD_TEST(suite, test_building_set_owner);
+  SUITE_ADD_TEST(suite, test_buildingowner_resets_when_dead);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_next_after_death);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_other_after_death);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_same_faction_after_death);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_next_after_leave);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_other_after_leave);
+  SUITE_ADD_TEST(suite, test_buildingowner_goes_to_same_faction_after_leave);
+  return suite;
+}
diff --git a/src/kernel/ship.c b/src/kernel/ship.c
index 966074a27..2d15bb52c 100644
--- a/src/kernel/ship.c
+++ b/src/kernel/ship.c
@@ -278,39 +278,39 @@ void getshipweight(const ship * sh, int *sweight, int *scabins)
 
 void ship_set_owner(ship * sh, unit * u) {
   assert(u->ship==sh);
-  if (sh->owner && sh->owner!=u) {
-    freset(sh->owner, UFL_OWNER);
+  if (sh->_owner && sh->_owner!=u) {
+    freset(sh->_owner, UFL_OWNER);
   }
-  sh->owner = u;
+  sh->_owner = u;
   fset(u, UFL_OWNER);
 }
 
-unit *ship_owner(ship * sh)
+unit *ship_owner(const ship * sh)
 {
-  unit *owner = sh->owner;
-  if (owner && owner->number<=0) {
-    unit *u, *first = NULL;
+  unit *owner = sh->_owner;
+  if (owner && (owner->ship!=sh || owner->number<=0)) {
+    unit *u, *heir = 0;
 
     owner->ship = 0;
-    freset(owner, UFL_OWNER);
     /* Prüfen ob Eigentümer am leben. */
     for (u = sh->region->units; u; u = u->next) {
       if (u->ship == sh) {
         if (u->number > 0) {
           if (u->faction==owner->faction) {
-            first = u;
+            heir = u;
             break;
           }
-          else if (!first) {
-            first = u; /* you'll do in an emergency */
+          else if (!heir) {
+            heir = u; /* you'll do in an emergency */
           }
         }
+        freset(u, UFL_OWNER);
       }
     }
-    owner = first;
+    freset(owner, UFL_OWNER);
+    owner = heir;
     if (owner) {
       fset(owner, UFL_OWNER);
-      sh->owner = owner;
     }
   }
   /* Eigentümer tot oder kein Eigentümer vorhanden. Erste lebende Einheit
diff --git a/src/kernel/ship.h b/src/kernel/ship.h
index aedbff63c..b4e95a302 100644
--- a/src/kernel/ship.h
+++ b/src/kernel/ship.h
@@ -81,7 +81,7 @@ extern "C" {
   typedef struct ship {
     struct ship *next;
     struct ship *nexthash;
-    struct unit * owner;
+    struct unit * _owner; /* never use directly, always use ship_owner() */
     int no;
     struct region *region;
     char *name;
@@ -96,7 +96,7 @@ extern "C" {
 
   extern void damage_ship(struct ship * sh, double percent);
   extern void ship_set_owner(struct ship * sh, struct unit * u);
-  extern struct unit *ship_owner(struct ship *sh);
+  extern struct unit *ship_owner(const struct ship *sh);
   extern const char *shipname(const struct ship *self);
   extern int shipcapacity(const struct ship *sh);
   extern void getshipweight(const struct ship *sh, int *weight, int *cabins);
diff --git a/src/kernel/ship_test.c b/src/kernel/ship_test.c
index 9eb6641a3..8e69a6bd4 100644
--- a/src/kernel/ship_test.c
+++ b/src/kernel/ship_test.c
@@ -1,5 +1,6 @@
 #include <platform.h>
 
+#include <kernel/config.h>
 #include <kernel/types.h>
 #include <kernel/race.h>
 #include <kernel/region.h>
@@ -43,8 +44,10 @@ static void test_ship_set_owner(CuTest * tc)
 
   sh = test_create_ship(r, stype);
   u1 = test_create_unit(f, r);
-  u2 = test_create_unit(f, r);
   u_set_ship(u1, sh);
+  CuAssertPtrEquals(tc, u1, ship_owner(sh));
+
+  u2 = test_create_unit(f, r);
   u_set_ship(u2, sh);
   CuAssertPtrEquals(tc, u1, ship_owner(sh));
   ship_set_owner(sh, u2);
diff --git a/src/kernel/unit.c b/src/kernel/unit.c
index 07f80c410..3b1fdcf3b 100644
--- a/src/kernel/unit.c
+++ b/src/kernel/unit.c
@@ -778,17 +778,17 @@ void u_set_building(unit * u, building * b)
 {
   assert(b && !u->building); /* you must leave first */
   u->building = b;
+  if (b && !b->_owner) {
+    building_set_owner(b, u);
+  }
 }
 
 void u_set_ship(unit * u, ship * sh)
 {
   assert(!u->ship); /* you must leave_ship */
-  if (sh) {
-    u->ship = sh;
-    if (!sh->owner) {
-      sh->owner = u;
-      fset(u, UFL_OWNER);
-    }
+  u->ship = sh;
+  if (sh && !sh->_owner) {
+    ship_set_owner(sh, u);
   }
 }
 
@@ -798,37 +798,14 @@ void leave_ship(unit * u)
   if (!sh) return;
   u->ship = 0;
   set_leftship(u, sh);
-
-  if (fval(u, UFL_OWNER)) {
-    unit *u2, *owner = NULL;
-    freset(u, UFL_OWNER);
-
-    for (u2 = u->region->units; u2; u2 = u2->next) {
-      if (u2->ship == sh) {
-        if (u2->faction == u->faction) {
-          owner = u2;
-          break;
-        } else if (!owner) {
-          owner = u2;
-        }
-      }
-    }
-    sh->owner = owner;
-    if (owner) {
-      fset(owner, UFL_OWNER);
-    }
-  }
-  assert(sh->owner!=u);
 }
 
 void leave_building(unit * u)
 {
   struct building *b = u->building;
-  if (!b)
-    return;
-  u->building = NULL;
 
-  if (fval(u, UFL_OWNER)) {
+  u->building = NULL;
+  if (b && fval(u, UFL_OWNER)) {
     unit *u2, *owner = NULL;
     freset(u, UFL_OWNER);
 
@@ -1521,7 +1498,9 @@ unit *create_unit(region * r, faction * f, int number, const struct race *urace,
 
     /* erbt Gebäude/Schiff */
     if (creator->region == r) {
-      u->building = creator->building;
+      if (creator->building) {
+        u_set_building(u, creator->building);
+      }
       if (creator->ship && fval(u->race, RCF_CANSAIL)) {
         u_set_ship(u, creator->ship);
       }
diff --git a/src/tests.c b/src/tests.c
index e55f31825..5219f9983 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -10,6 +10,7 @@
 #include <util/umlaut_test.c>
 #include <kernel/move_test.c>
 #include <kernel/ship_test.c>
+#include <kernel/building_test.c>
 #include <kernel/spell_test.c>
 #include <kernel/curse_test.c>
 #include <kernel/battle_test.c>
@@ -47,6 +48,7 @@ int RunAllTests(void)
   CuSuiteAddSuite(suite, get_move_suite());
   CuSuiteAddSuite(suite, get_reports_suite());
   CuSuiteAddSuite(suite, get_ship_suite());
+  CuSuiteAddSuite(suite, get_building_suite());
   CuSuiteAddSuite(suite, get_spell_suite());
   CuSuiteAddSuite(suite, get_laws_suite());
   CuSuiteAddSuite(suite, get_battle_suite());