diff --git a/src/kernel/item.c b/src/kernel/item.c
index fd35f0776..2fd76ded3 100644
--- a/src/kernel/item.c
+++ b/src/kernel/item.c
@@ -1226,6 +1226,10 @@ void test_clear_resources(void)
 
 void register_resources(void)
 {
+  static bool registered = false;
+  if (registered) return;
+  registered = true;
+
   register_function((pf_generic) mod_elves_only, "mod_elves_only");
   register_function((pf_generic) mod_dwarves_only, "mod_dwarves_only");
   register_function((pf_generic) res_changeitem, "changeitem");
diff --git a/src/kernel/item_test.c b/src/kernel/item_test.c
index c59e47d33..6279bc0af 100644
--- a/src/kernel/item_test.c
+++ b/src/kernel/item_test.c
@@ -2,11 +2,35 @@
 
 #include <kernel/types.h>
 #include <kernel/item.h>
+#include <kernel/unit.h>
 #include <util/language.h>
+#include <util/functions.h>
 
 #include <CuTest.h>
 #include <tests.h>
 
+void test_change_item(CuTest * tc)
+{
+  rtype_uchange res_changeitem;
+  const resource_type * rtype;
+  unit * u;
+
+  register_resources();
+  res_changeitem = (rtype_uchange)get_function("changeitem");
+  CuAssertPtrNotNull(tc, res_changeitem);
+
+  test_cleanup();
+  test_create_world();
+  rtype = olditemtype[I_IRON]->rtype;
+
+  u = test_create_unit(0, 0);
+  CuAssertIntEquals(tc, 0, res_changeitem(u, rtype, 0));
+  i_change(&u->items, rtype->itype, 4);
+  CuAssertIntEquals(tc, 4, res_changeitem(u, rtype, 0));
+  CuAssertIntEquals(tc, 1, res_changeitem(u, rtype, -3));
+  CuAssertIntEquals(tc, 1, i_get(u->items, rtype->itype));
+}
+
 void test_resource_type(CuTest * tc)
 {
   struct item_type *itype;
@@ -68,6 +92,7 @@ void test_findresourcetype(CuTest * tc)
 CuSuite *get_item_suite(void)
 {
   CuSuite *suite = CuSuiteNew();
+  SUITE_ADD_TEST(suite, test_change_item);
   SUITE_ADD_TEST(suite, test_resource_type);
   SUITE_ADD_TEST(suite, test_finditemtype);
   SUITE_ADD_TEST(suite, test_findresourcetype);
diff --git a/src/tests.c b/src/tests.c
index dd05c7d93..568e65ac4 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -180,15 +180,15 @@ void test_create_world(void)
   terrain_type *t_plain, *t_ocean;
   region *island[2];
   int i;
-  item_type * itype;
-  const char * names[] = { "horse", "horse_p", "boat", "boat_p" };
+  const char * names[] = { "horse", "horse_p", "boat", "boat_p", "iron", "iron_p", "stone", "stone_p" };
 
   make_locale("de");
   init_resources();
   assert(!olditemtype[I_HORSE]);
 
-  itype = test_create_itemtype(names);
-  olditemtype[I_HORSE] = itype;
+  olditemtype[I_HORSE] = test_create_itemtype(names+0);
+  olditemtype[I_IRON] = test_create_itemtype(names+4);
+  olditemtype[I_STONE] = test_create_itemtype(names+6);
 
   t_plain = test_create_terrain("plain", LAND_REGION | FOREST_REGION | WALK_INTO | CAVALRY_REGION);
   t_plain->size = 1000;