diff --git a/C/init.c b/C/init.c
index 86d9ee51b..638e23574 100644
--- a/C/init.c
+++ b/C/init.c
@@ -963,6 +963,9 @@ InitFlags(void)
 static void 
 InitCodes(void)
 {
+  /* initialise invisible chain */
+  Yap_heap_regs->invisiblechain.Entry = NIL;
+  INIT_RWLOCK(Yap_heap_regs->invisiblechain.AERWLock);
 #include "iatoms.h"
   Yap_heap_regs->term_prolog = MkAtomTerm(AtomProlog);
   Yap_heap_regs->user_module = MkAtomTerm(AtomUser);
@@ -1136,9 +1139,6 @@ InitCodes(void)
   Yap_heap_regs->clausecode->clause = NULL;
   Yap_heap_regs->clausecode->func = NIL;
 
-  Yap_heap_regs->invisiblechain.Entry = NIL;
-  INIT_RWLOCK(Yap_heap_regs->invisiblechain.AERWLock);
-  
   {
     Atom            at;
     PredEntry      *pred;
diff --git a/H/Heap.h b/H/Heap.h
index c64152913..79deee11f 100644
--- a/H/Heap.h
+++ b/H/Heap.h
@@ -14,7 +14,6 @@
 *************************************************************************/
 
 /* information that can be stored in Code Space */
-#include <stdio.h>
 
 #ifndef HEAP_H
 #define HEAP_H 1
@@ -814,27 +813,4 @@ Yap_PreAllocCodeSpace(void)
   return Yap_InitPreAllocCodeSpace();
 }
 
-#ifdef ATOMS_H
-#ifdef THREADS
-Prop STD_PROTO(Yap_NewThreadPred, (struct pred_entry *));
-Prop STD_PROTO(Yap_NewPredPropByFunctor, (Functor, Term));
-
-EXTERN inline PredEntry *
-Yap_GetThreadPred(struct pred_entry *ap)
-{
-  Functor f = ap->FunctorOfPred;
-  Term  mod = ap->ModuleOfPred;
-  Prop p0 = AbsPredProp(Yap_heap_regs->thread_handle[worker_id].local_preds);
-
-  while(p0) {
-    PredEntry *ap = RepPredProp(p0);
-    if (ap->FunctorOfPred == f &&
-	ap->ModuleOfPred == mod) return ap;
-    p0 = ap->NextOfPE;
-  }
-  return RepPredProp(Yap_NewThreadPred(ap));
-}
-#endif
-#endif
-
 #endif /* HEAP_H */
diff --git a/H/Yatom.h b/H/Yatom.h
index 692eb7c68..8bcb14374 100644
--- a/H/Yatom.h
+++ b/H/Yatom.h
@@ -17,6 +17,9 @@
 
 /* This code can only be defined *after* including Regs.h!!! */
 
+#ifndef YATOM_H
+#define YATOM_H 1
+
 #ifdef USE_OFFSETS
 
 inline EXTERN Atom AbsAtom (AtomEntry * p);
@@ -1369,10 +1372,6 @@ Atom STD_PROTO (Yap_GetOp, (OpEntry *, int *, int));
 Prop STD_PROTO (Yap_GetAProp, (Atom, PropFlags));
 Prop STD_PROTO (Yap_GetAPropHavingLock, (AtomEntry *, PropFlags));
 
-#ifdef THREADS
-EXTERN inline PredEntry *STD_PROTO (Yap_GetThreadPred, (PredEntry *));
-#endif
-
 typedef enum
 {
   PROLOG_MODULE = 0,
@@ -1395,6 +1394,30 @@ PRED_HASH(FunctorEntry *fe, Term cur_mod, UInt size)
 
 EXTERN inline Prop STD_PROTO(GetPredPropByFuncHavingLock, (FunctorEntry *, Term));
 
+#ifdef THREADS
+
+Prop STD_PROTO(Yap_NewThreadPred, (struct pred_entry *));
+Prop STD_PROTO(Yap_NewPredPropByFunctor, (Functor, Term));
+EXTERN inline struct pred_entry *STD_PROTO(Yap_GetThreadPred, (struct pred_entry *));
+
+EXTERN inline struct pred_entry *
+Yap_GetThreadPred(struct pred_entry *ap)
+{
+  Functor f = ap->FunctorOfPred;
+  Term  mod = ap->ModuleOfPred;
+  Prop p0 = AbsPredProp(Yap_heap_regs->thread_handle[worker_id].local_preds);
+
+  while(p0) {
+    PredEntry *ap = RepPredProp(p0);
+    if (ap->FunctorOfPred == f &&
+	ap->ModuleOfPred == mod) return ap;
+    p0 = ap->NextOfPE;
+  }
+  return RepPredProp(Yap_NewThreadPred(ap));
+}
+#endif
+
+
 EXTERN inline Prop
 GetPredPropByFuncHavingLock (FunctorEntry *fe, Term cur_mod)
 {
@@ -1484,3 +1507,4 @@ PredPropByAtom (Atom at, Term cur_mod)
   return Yap_NewPredPropByAtom (ae, cur_mod);
 }
 
+#endif
diff --git a/H/threads.h b/H/threads.h
index 30b704774..4569198dc 100644
--- a/H/threads.h
+++ b/H/threads.h
@@ -1,3 +1,10 @@
+
+#ifndef THREADS_H
+
+#define THREADS_H 1
+
+#ifdef THREADS
+
 typedef struct{
   UInt		    ssize;
   UInt		    tsize;
@@ -14,3 +21,6 @@ Int STD_PROTO(Yap_thread_attach_engine,(int));
 Int STD_PROTO(Yap_thread_detach_engine,(int));
 Int STD_PROTO(Yap_thread_destroy_engine,(int));
 
+#endif
+
+#endif