diff --git a/src/l52util.c b/src/l52util.c
index 6373687..4883a9e 100644
--- a/src/l52util.c
+++ b/src/l52util.c
@@ -13,6 +13,7 @@
 #include <memory.h>
 #include <string.h> /* for memset */
 #include <assert.h>
+#include <luajit.h> /* for LUAJIT_VERSION: LuaJIT already provides luaL_setfuncs */
 
 #if LUA_VERSION_NUM >= 502 
 
@@ -31,8 +32,12 @@ void luaL_register (lua_State *L, const char *libname, const luaL_Reg *l){
 
 #endif
 
-#else 
+#else
 
+#ifndef LUAJIT_VERSION
+/* LuaJIT's own lib_aux.c already provides luaL_setfuncs (declared in
+ * lauxlib.h); defining it again here would collide at link time when
+ * LuaJIT is linked as a static library. Only needed for vanilla Lua 5.1. */
 void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup){
   luaL_checkstack(L, nup, "too many upvalues");
   for (; l->name != NULL; l++) {  /* fill the table with given functions */
@@ -44,6 +49,7 @@ void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup){
   }
   lua_pop(L, nup);  /* remove upvalues */
 }
+#endif
 
 void lua_rawgetp(lua_State *L, int index, const void *p){
   index = lua_absindex(L, index);