diff --git a/src/give.test.c b/src/give.test.c
index 604e42549..33a9ebfd9 100644
--- a/src/give.test.c
+++ b/src/give.test.c
@@ -88,6 +88,7 @@ static void test_give_unit_limits(CuTest * tc) {
     CuAssertIntEquals(tc, 0, env.f2->newbies);
     CuAssertIntEquals(tc, 1, env.f1->num_units);
     CuAssertIntEquals(tc, 1, env.f2->num_units);
+    CuAssertPtrNotNull(tc, test_find_messagetype(env.f1->msgs, "too_many_units_in_faction"));
     test_cleanup();
 }
 
diff --git a/src/kernel/alliance.c b/src/kernel/alliance.c
index 0feb8407d..910670d10 100644
--- a/src/kernel/alliance.c
+++ b/src/kernel/alliance.c
@@ -239,8 +239,25 @@ static void perform_transfer(void)
     }
 }
 
+bool num_units_cb(void *entry, void *more) {
+    faction *f = (faction *)entry;
+    int *num = (int *)more;
+    *num += f->num_units;
+    return true;
+}
+
+int alliance_size(const alliance *al)
+{
+    int num = 0;
+    if (al) {
+        selist_foreach_ex(al->members, num_units_cb, &num);
+    }
+    return num;
+}
+
 static void perform_join(void)
 {
+    int alimit = rule_alliance_limit();
     alliance_transaction **tap = transactions + ALLIANCE_JOIN;
     while (*tap) {
         alliance_transaction *ta = *tap;
@@ -270,7 +287,16 @@ static void perform_join(void)
                     ti = *tip;
                 }
                 if (ti) {
-                    setalliance(fj, al);
+                    int maxsize = (alimit > 0) ? (alimit - alliance_size(al)) : 0;
+                    if (alimit > 0 && fj->num_units > maxsize) {
+                        ADDMSG(&fj->msgs,
+                            msg_feedback(ta->u, ta->ord,
+                                "too_many_units_in_alliance",
+                                "allowed", alimit));
+                    }
+                    else {
+                        setalliance(fj, al);
+                    }
                     *tip = ti->next;
                     free(ti);
                 }
diff --git a/src/kernel/alliance.h b/src/kernel/alliance.h
index 8e112e8c9..00b4b29e4 100644
--- a/src/kernel/alliance.h
+++ b/src/kernel/alliance.h
@@ -67,7 +67,7 @@ extern "C" {
     struct faction *alliance_get_leader(struct alliance *al);
     void alliance_cmd(void);
     bool is_allied(const struct faction *f1, const struct faction *f2);
-
+    int alliance_size(const struct alliance *al); /* #units in the alliance */
     void alliance_setname(alliance * self, const char *name);
     /* execute commands */
 
diff --git a/src/kernel/alliance.test.c b/src/kernel/alliance.test.c
index f63767672..885bc8413 100644
--- a/src/kernel/alliance.test.c
+++ b/src/kernel/alliance.test.c
@@ -112,6 +112,29 @@ static void test_alliance_cmd(CuTest *tc) {
     test_cleanup();
 }
 
+static void test_alliance_limits(CuTest *tc) {
+    unit *u1, *u2;
+    struct region *r;
+
+    test_setup();
+    r = test_create_region(0, 0, 0);
+    u1 = test_create_unit(test_create_faction(0), r);
+    u2 = test_create_unit(test_create_faction(0), r);
+
+    config_set("rules.limit.alliance", "1");
+    unit_addorder(u1, create_order(K_ALLIANCE, u1->faction->locale, "%s %s", alliance_kwd[ALLIANCE_NEW], itoa36(42)));
+    unit_addorder(u1, create_order(K_ALLIANCE, u1->faction->locale, "%s %s", alliance_kwd[ALLIANCE_INVITE], itoa36(u2->faction->no)));
+    unit_addorder(u2, create_order(K_ALLIANCE, u1->faction->locale, "%s %s", alliance_kwd[ALLIANCE_JOIN], itoa36(42)));
+    CuAssertTrue(tc, !is_allied(u1->faction, u2->faction));
+    CuAssertPtrEquals(tc, 0, f_get_alliance(u1->faction));
+    alliance_cmd();
+    CuAssertPtrNotNull(tc, f_get_alliance(u1->faction));
+    CuAssertPtrEquals(tc, 0, f_get_alliance(u2->faction));
+    CuAssertTrue(tc, !is_allied(u1->faction, u2->faction));
+    CuAssertPtrNotNull(tc, test_find_messagetype(u2->faction->msgs, "too_many_units_in_alliance"));
+    test_cleanup();
+}
+
 static void test_alliance_cmd_kick(CuTest *tc) {
     unit *u1, *u2;
     struct region *r;
@@ -200,6 +223,7 @@ CuSuite *get_alliance_suite(void)
     SUITE_ADD_TEST(suite, test_alliance_dead_faction);
     SUITE_ADD_TEST(suite, test_alliance_make);
     SUITE_ADD_TEST(suite, test_alliance_join);
+    SUITE_ADD_TEST(suite, test_alliance_limits);
     SUITE_ADD_TEST(suite, test_alliance_cmd);
     SUITE_ADD_TEST(suite, test_alliance_cmd_no_invite);
     SUITE_ADD_TEST(suite, test_alliance_cmd_kick);
diff --git a/src/laws.c b/src/laws.c
index 9c25ac461..736510cd2 100644
--- a/src/laws.c
+++ b/src/laws.c
@@ -3028,20 +3028,10 @@ int checkunitnumber(const faction * f, int add)
 
     alimit = rule_alliance_limit();
     if (alimit) {
-        faction *f2;
-        int unitsinalliance = fno;
-        if (unitsinalliance > alimit) {
+        int unitsinalliance = alliance_size(f->alliance);
+        if (unitsinalliance + add > alimit) {
             return 1;
         }
-
-        for (f2 = factions; f2; f2 = f2->next) {
-            if (f != f2 && f->alliance == f2->alliance) {
-                unitsinalliance += f2->num_units;
-                if (unitsinalliance > alimit) {
-                    return 1;
-                }
-            }
-        }
     }
 
     return 0;