diff --git a/src/kernel/building.c b/src/kernel/building.c
index f2c9c9fd2..98caad07a 100644
--- a/src/kernel/building.c
+++ b/src/kernel/building.c
@@ -335,7 +335,18 @@ const building_type *findbuildingtype(const char *name,
     return (const building_type *)type.v;
 }
 
-static int building_protection(const building * b, const unit * u, building_bonus bonus)
+int cmp_castle_size(const building * b, const building * a)
+{
+    if (!b || !b->type->protection || !building_owner(b)) {
+        return -1;
+    }
+    if (!a || !a->type->protection || !building_owner(a)) {
+        return 1;
+    }
+    return b->size - a->size;
+}
+
+int building_protection(const building * b, const unit * u, building_bonus bonus)
 {
     int i = 0;
     int bsize = buildingeffsize(b, false);
diff --git a/src/kernel/building.h b/src/kernel/building.h
index a6936d90d..8b1a5b05b 100644
--- a/src/kernel/building.h
+++ b/src/kernel/building.h
@@ -85,6 +85,8 @@ extern "C" {
     extern struct selist *buildingtypes;
     extern struct attrib_type at_building_action;
 
+    int cmp_castle_size(const struct building * b, const struct building * a);
+    int building_protection(const struct building * b, const struct unit * u, building_bonus bonus);
     building_type *bt_get_or_create(const char *name);
     bool bt_changed(int *cache);
     const building_type *bt_find(const char *name);
diff --git a/src/kernel/building.test.c b/src/kernel/building.test.c
index 3b296a6fe..89e2b978c 100644
--- a/src/kernel/building.test.c
+++ b/src/kernel/building.test.c
@@ -493,9 +493,35 @@ static void test_building_type(CuTest *tc) {
     test_cleanup();
 }
 
+static void test_cmp_castle_size(CuTest *tc) {
+    region *r;
+    building *b1, *b2;
+    building_type *bt_castle;
+    unit *u1, *u2;
+
+    test_setup();
+    bt_castle = test_create_buildingtype("castle");
+    bt_castle->protection = building_protection;
+    r = test_create_region(0, 0, 0);
+    b1 = test_create_building(r, bt_castle);
+    b2 = test_create_building(r, bt_castle);
+    u1 = test_create_unit(test_create_faction(0), r);
+    u_set_building(u1, b1);
+    u2 = test_create_unit(test_create_faction(0), r);
+    u_set_building(u2, b2);
+    b1->size = 5;
+    b2->size = 10;
+    CuAssertTrue(tc, cmp_castle_size(b1, b2)<0);
+    CuAssertTrue(tc, cmp_castle_size(b2, b1)>0);
+    CuAssertTrue(tc, cmp_castle_size(b1, NULL)>0);
+    CuAssertTrue(tc, cmp_castle_size(NULL, b1)<0);
+    test_cleanup();
+}
+
 CuSuite *get_building_suite(void)
 {
     CuSuite *suite = CuSuiteNew();
+    SUITE_ADD_TEST(suite, test_cmp_castle_size);
     SUITE_ADD_TEST(suite, test_register_building);
     SUITE_ADD_TEST(suite, test_btype_defaults);
     SUITE_ADD_TEST(suite, test_building_set_owner);
diff --git a/src/kernel/region.c b/src/kernel/region.c
index cade135c7..06d2d9d7c 100644
--- a/src/kernel/region.c
+++ b/src/kernel/region.c
@@ -1324,9 +1324,17 @@ struct message *msg)
 
 struct faction *region_get_owner(const struct region *r)
 {
-    assert(rule_region_owners());
-    if (r->land && r->land->ownership) {
-        return r->land->ownership->owner;
+    if (r->land) {
+        if (rule_region_owners()) {
+            if (r->land->ownership) {
+                return r->land->ownership->owner;
+            }
+        }
+        else {
+            building *b = largestbuilding(r, cmp_castle_size, false);
+            unit * u = b ? building_owner(b) : NULL;
+            return u ? u->faction : NULL;
+        }
     }
     return NULL;
 }
diff --git a/src/kernel/region.test.c b/src/kernel/region.test.c
index 01ecae2a8..8cf08a62c 100644
--- a/src/kernel/region.test.c
+++ b/src/kernel/region.test.c
@@ -1,6 +1,8 @@
 #include <platform.h>
 
 #include "region.h"
+#include "building.h"
+#include "unit.h"
 #include "terrain.h"
 #include "item.h"
 
@@ -31,9 +33,32 @@ void test_terraform(CuTest *tc) {
     test_cleanup();
 }
 
+static void test_region_get_owner(CuTest *tc) {
+    region *r;
+    building *b1, *b2;
+    building_type *bt_castle;
+    unit *u1, *u2;
+
+    test_setup();
+    bt_castle = test_create_buildingtype("castle");
+    bt_castle->protection = building_protection;
+    r = test_create_region(0, 0, 0);
+    b1 = test_create_building(r, bt_castle);
+    b2 = test_create_building(r, bt_castle);
+    b1->size = 5;
+    b2->size = 10;
+    u1 = test_create_unit(test_create_faction(0), r);
+    u_set_building(u1, b1);
+    u2 = test_create_unit(test_create_faction(0), r);
+    u_set_building(u2, b2);
+    CuAssertPtrEquals(tc, u2->faction, region_get_owner(r));
+    test_cleanup();
+}
+
 CuSuite *get_region_suite(void)
 {
     CuSuite *suite = CuSuiteNew();
     SUITE_ADD_TEST(suite, test_terraform);
+    SUITE_ADD_TEST(suite, test_region_get_owner);
     return suite;
 }