diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 663b54bd1..ddab0d321 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -113,6 +113,7 @@ set (ERESSEA_SRC
   renumber.c
   report.c
   reports.c
+  sort.c
   spells.c
   spy.c
   steal.c
@@ -237,6 +238,7 @@ set(TESTS_SRC
   renumber.test.c
   report.test.c
   reports.test.c
+  sort.test.c
   spells.test.c
   spy.test.c
   study.test.c
diff --git a/src/bind_process.c b/src/bind_process.c
index 8626a2820..974bba4bd 100755
--- a/src/bind_process.c
+++ b/src/bind_process.c
@@ -10,6 +10,7 @@
 #include "magic.h"
 #include "market.h"
 #include "move.h"
+#include "sort.h"
 #include "study.h"
 
 #include <kernel/alliance.h>
diff --git a/src/laws.c b/src/laws.c
index d9ec9afca..373bbfb62 100644
--- a/src/laws.c
+++ b/src/laws.c
@@ -19,6 +19,7 @@
 #include "randenc.h"
 #include "recruit.h"
 #include "renumber.h"
+#include "sort.h"
 #include "spy.h"
 #include "study.h"
 #include "wormhole.h"
@@ -2631,93 +2632,6 @@ void sinkships(struct region * r)
     }
 }
 
-void restack_units(void)
-{
-    region *r;
-    for (r = regions; r; r = r->next) {
-        unit **up = &r->units;
-        bool sorted = false;
-        while (*up) {
-            unit *u = *up;
-            if (!fval(u, UFL_MARK)) {
-                struct order *ord;
-                for (ord = u->orders; ord; ord = ord->next) {
-                    if (getkeyword(ord) == K_SORT) {
-                        char token[128];
-                        const char *s;
-                        param_t p;
-                        int id;
-                        unit *v;
-
-                        init_order(ord, NULL);
-                        s = gettoken(token, sizeof(token));
-                        p = findparam(s, u->faction->locale);
-                        id = getid();
-                        v = findunit(id);
-
-                        if (!v || v->faction != u->faction || v->region != r) {
-                            cmistake(u, ord, 258, MSG_EVENT);
-                        }
-                        else if (v->building != u->building || v->ship != u->ship) {
-                            cmistake(u, ord, 259, MSG_EVENT);
-                        }
-                        else if (u->building && building_owner(u->building) == u) {
-                            cmistake(u, ord, 260, MSG_EVENT);
-                        }
-                        else if (u->ship && ship_owner(u->ship) == u) {
-                            cmistake(u, ord, 260, MSG_EVENT);
-                        }
-                        else if (v == u) {
-                            syntax_error(u, ord);
-                        }
-                        else {
-                            switch (p) {
-                            case P_AFTER:
-                                *up = u->next;
-                                u->next = v->next;
-                                v->next = u;
-                                fset(u, UFL_MARK);
-                                sorted = true;
-                                break;
-                            case P_BEFORE:
-                                if (v->ship && ship_owner(v->ship) == v) {
-                                    cmistake(v, ord, 261, MSG_EVENT);
-                                }
-                                else if (v->building && building_owner(v->building) == v) {
-                                    cmistake(v, ord, 261, MSG_EVENT);
-                                }
-                                else {
-                                    unit **vp = &r->units;
-                                    while (*vp != v)
-                                        vp = &(*vp)->next;
-                                    *vp = u;
-                                    *up = u->next;
-                                    u->next = v;
-                                }
-                                fset(u, UFL_MARK);
-                                sorted = true;
-                                break;
-                            default:
-                                /* TODO: syntax error message? */
-                                break;
-                            }
-                        }
-                        break;
-                    }
-                }
-            }
-            if (u == *up)
-                up = &u->next;
-        }
-        if (sorted) {
-            unit *u;
-            for (u = r->units; u; u = u->next) {
-                freset(u, UFL_MARK);
-            }
-        }
-    }
-}
-
 /* blesses stone circles create an astral protection in the astral region
  * above the shield, which prevents chaos suction and other spells.
  * The shield is created when a magician enters the blessed stone circle,
diff --git a/src/laws.h b/src/laws.h
index 5bf81440d..521e28f2b 100755
--- a/src/laws.h
+++ b/src/laws.h
@@ -44,7 +44,6 @@ extern "C" {
     void defaultorders(void);
     void quit(void);
     void monthly_healing(void);
-    void restack_units(void);
     void update_long_order(struct unit *u);
     void sinkships(struct region * r);
     void do_enter(struct region *r, bool is_final_attempt);
diff --git a/src/laws.test.c b/src/laws.test.c
index c51939fa2..cf57224d5 100644
--- a/src/laws.test.c
+++ b/src/laws.test.c
@@ -1379,7 +1379,7 @@ static void test_ally_cmd(CuTest *tc) {
     order *ord;
 
     test_setup();
-    u = test_create_unit(test_create_faction(), test_create_region(0, 0, NULL));
+    u = test_create_unit(test_create_faction(), test_create_plain(0, 0));
     f = test_create_faction();
 
     ord = create_order(K_ALLY, f->locale, "%s", itoa36(f->no));
diff --git a/src/sort.c b/src/sort.c
new file mode 100644
index 000000000..17da43563
--- /dev/null
+++ b/src/sort.c
@@ -0,0 +1,102 @@
+#include "sort.h"
+
+#include "kernel/config.h"
+#include "kernel/building.h"
+#include "kernel/faction.h"
+#include "kernel/messages.h"
+#include "kernel/order.h"
+#include "kernel/region.h"
+#include "kernel/ship.h"
+#include "kernel/unit.h"
+
+#include "util/keyword.h"
+#include "util/param.h"
+#include "util/parser.h"
+
+void restack_units(void)
+{
+    region *r;
+    for (r = regions; r; r = r->next) {
+        unit **up = &r->units;
+        bool sorted = false;
+        while (*up) {
+            unit *u = *up;
+            if (!fval(u, UFL_MARK)) {
+                struct order *ord;
+                for (ord = u->orders; ord; ord = ord->next) {
+                    if (getkeyword(ord) == K_SORT) {
+                        char token[128];
+                        const char *s;
+                        param_t p;
+                        int id;
+                        unit *v;
+
+                        init_order(ord, NULL);
+                        s = gettoken(token, sizeof(token));
+                        p = findparam(s, u->faction->locale);
+                        id = getid();
+                        v = findunit(id);
+
+                        if (!v || v->faction != u->faction || v->region != r) {
+                            cmistake(u, ord, 258, MSG_EVENT);
+                        }
+                        else if (v->building != u->building || v->ship != u->ship) {
+                            cmistake(u, ord, 259, MSG_EVENT);
+                        }
+                        else if (u->building && building_owner(u->building) == u) {
+                            cmistake(u, ord, 260, MSG_EVENT);
+                        }
+                        else if (u->ship && ship_owner(u->ship) == u) {
+                            cmistake(u, ord, 260, MSG_EVENT);
+                        }
+                        else if (v == u) {
+                            syntax_error(u, ord);
+                        }
+                        else {
+                            switch (p) {
+                            case P_AFTER:
+                                *up = u->next;
+                                u->next = v->next;
+                                v->next = u;
+                                fset(u, UFL_MARK);
+                                sorted = true;
+                                break;
+                            case P_BEFORE:
+                                if (v->ship && ship_owner(v->ship) == v) {
+                                    cmistake(v, ord, 261, MSG_EVENT);
+                                }
+                                else if (v->building && building_owner(v->building) == v) {
+                                    cmistake(v, ord, 261, MSG_EVENT);
+                                }
+                                else {
+                                    unit **vp = &r->units;
+                                    while (*vp != v)
+                                        vp = &(*vp)->next;
+                                    *vp = u;
+                                    *up = u->next;
+                                    u->next = v;
+                                }
+                                fset(u, UFL_MARK);
+                                sorted = true;
+                                break;
+                            default:
+                                /* TODO: syntax error message? */
+                                break;
+                            }
+                        }
+                        break;
+                    }
+                }
+            }
+            if (u == *up)
+                up = &u->next;
+        }
+        if (sorted) {
+            unit *u;
+            for (u = r->units; u; u = u->next) {
+                freset(u, UFL_MARK);
+            }
+        }
+    }
+}
+
diff --git a/src/sort.h b/src/sort.h
new file mode 100644
index 000000000..d2228fa1c
--- /dev/null
+++ b/src/sort.h
@@ -0,0 +1,3 @@
+#pragma once
+
+void restack_units(void);
diff --git a/src/sort.test.c b/src/sort.test.c
new file mode 100644
index 000000000..5e085ec2c
--- /dev/null
+++ b/src/sort.test.c
@@ -0,0 +1,67 @@
+#include "sort.h"
+
+#include "kernel/faction.h"
+#include "kernel/unit.h"
+#include "kernel/order.h"
+#include "kernel/region.h"
+
+#include "util/base36.h"
+#include "util/keyword.h"
+#include "util/language.h"
+#include "util/param.h"
+
+#include "tests.h"
+#include <CuTest.h>
+
+static void test_sort_after(CuTest *tc) {
+    unit *u1, *u2;
+    faction *f;
+    region *r;
+
+    test_setup();
+    u1 = test_create_unit(f = test_create_faction(), r = test_create_plain(0, 0));
+    u2 = test_create_unit(f, r);
+    unit_addorder(u1, create_order(K_SORT, f->locale, "%s %s",
+        LOC(f->locale, parameters[P_AFTER]), itoa36(u2->no)));
+    CuAssertPtrEquals(tc, u1, r->units);
+    CuAssertPtrEquals(tc, u2, u1->next);
+    CuAssertPtrEquals(tc, NULL, u2->next);
+
+    restack_units();
+    CuAssertPtrEquals(tc, u2, r->units);
+    CuAssertPtrEquals(tc, u1, u2->next);
+    CuAssertPtrEquals(tc, NULL, u1->next);
+
+    test_teardown();
+}
+
+static void test_sort_before(CuTest *tc) {
+    unit *u1, *u2;
+    faction *f;
+    region *r;
+
+    test_setup();
+    u1 = test_create_unit(f = test_create_faction(), r = test_create_plain(0, 0));
+    u2 = test_create_unit(f, r);
+    unit_addorder(u2, create_order(K_SORT, f->locale, "%s %s",
+        LOC(f->locale, parameters[P_BEFORE]), itoa36(u1->no)));
+    CuAssertPtrEquals(tc, u1, r->units);
+    CuAssertPtrEquals(tc, u2, u1->next);
+    CuAssertPtrEquals(tc, NULL, u2->next);
+
+    restack_units();
+    CuAssertPtrEquals(tc, u2, r->units);
+    CuAssertPtrEquals(tc, u1, u2->next);
+    CuAssertPtrEquals(tc, NULL, u1->next);
+
+    test_teardown();
+}
+
+
+CuSuite *get_sort_suite(void)
+{
+    CuSuite *suite = CuSuiteNew();
+    SUITE_ADD_TEST(suite, test_sort_after);
+    SUITE_ADD_TEST(suite, test_sort_before);
+    return suite;
+}
diff --git a/src/test_eressea.c b/src/test_eressea.c
index b644bc771..4c95e6582 100644
--- a/src/test_eressea.c
+++ b/src/test_eressea.c
@@ -146,6 +146,7 @@ int RunAllTests(int argc, char *argv[])
     ADD_SUITE(renumber);
     ADD_SUITE(report);
     ADD_SUITE(shock);
+    ADD_SUITE(sort);
     ADD_SUITE(spy);
     ADD_SUITE(stealth);
     ADD_SUITE(study);