diff --git a/src/helpers.c b/src/helpers.c
index 25079c549..7591dba9f 100644
--- a/src/helpers.c
+++ b/src/helpers.c
@@ -311,8 +311,8 @@ void register_tolua_helpers(void)
 
     callbacks.cast_spell = lua_callspell;
     callbacks.use_item = use_item_lua;
-    res_produce_fun = produce_resource_lua;
-    res_limit_fun = limit_resource_lua;
+    callbacks.produce_resource = produce_resource_lua;
+    callbacks.limit_resource = limit_resource_lua;
 
     register_function((pf_generic)lua_changeresource, "lua_changeresource");
     register_item_give(lua_giveitem, "lua_giveitem");
diff --git a/src/kernel/callbacks.h b/src/kernel/callbacks.h
index 0aa71daca..dcdf6ac90 100644
--- a/src/kernel/callbacks.h
+++ b/src/kernel/callbacks.h
@@ -26,13 +26,16 @@ extern "C" {
     struct castorder;
     struct order;
     struct unit;
+    struct region;
     struct item_type;
+    struct resource_type;
 
     struct callback_struct {
         int (*cast_spell)(struct castorder *co, const char *fname);
         int (*use_item)(struct unit *u, const struct item_type *itype,
             int amount, struct order *ord);
-
+        void(*produce_resource)(struct region *, const struct resource_type *, int);
+        int(*limit_resource)(const struct region *, const struct resource_type *);
     };
 
     extern struct callback_struct callbacks;
diff --git a/src/kernel/resources.c b/src/kernel/resources.c
index fe18ae640..842cb83ba 100644
--- a/src/kernel/resources.c
+++ b/src/kernel/resources.c
@@ -11,10 +11,11 @@
  */
 
 #include <platform.h>
-#include <kernel/config.h>
 #include "resources.h"
 
 /* kernel includes */
+#include <kernel/config.h>
+#include <kernel/callbacks.h>
 #include "build.h"
 #include "item.h"
 #include "region.h"
@@ -213,14 +214,11 @@ struct rawmaterial_type *rmt_create(struct resource_type *rtype)
     return rmtype;
 }
 
-int(*res_limit_fun)(const struct region *, const struct resource_type *);
-void(*res_produce_fun)(struct region *, const struct resource_type *, int);
-
 int limit_resource(const struct region *r, const resource_type *rtype)
 {
     assert(!rtype->raw);
-    if (res_limit_fun) {
-        return res_limit_fun(r, rtype);
+    if (callbacks.limit_resource) {
+        return callbacks.limit_resource(r, rtype);
     }
     return -1;
 }
@@ -228,7 +226,7 @@ int limit_resource(const struct region *r, const resource_type *rtype)
 void produce_resource(struct region *r, const struct resource_type *rtype, int amount)
 {
     assert(!rtype->raw);
-    if (res_produce_fun) {
-        res_produce_fun(r, rtype, amount);
+    if (callbacks.produce_resource) {
+        callbacks.produce_resource(r, rtype, amount);
     }
 }
diff --git a/src/kernel/resources.h b/src/kernel/resources.h
index e7a232d27..2daa44dd8 100644
--- a/src/kernel/resources.h
+++ b/src/kernel/resources.h
@@ -15,8 +15,11 @@
 extern "C" {
 #endif
 
+#include <util/variant.h>
+
     struct building_type;
     struct race;
+    struct region;
 
     enum {
         RM_USED = 1 << 0,           /* resource has been used */
@@ -71,8 +74,6 @@ extern "C" {
         int base, int divisor, const struct resource_type *rtype);
     struct rawmaterial_type *rmt_create(struct resource_type *rtype);
 
-    extern int(*res_limit_fun)(const struct region *, const struct resource_type *);
-    extern void(*res_produce_fun)(struct region *, const struct resource_type *, int);
     int limit_resource(const struct region *r, const struct resource_type *rtype);
     void produce_resource(struct region *r, const struct resource_type *rtype, int amount);