diff --git a/C/absmi.c b/C/absmi.c
index d5688fd21..74cb0b05c 100755
--- a/C/absmi.c
+++ b/C/absmi.c
@@ -1670,6 +1670,34 @@ Yap_absmi(int inp)
       ENDBOp();
 
 
+/*****************************************************************
+*        check for enough room			                 *
+*****************************************************************/
+
+      /* ensure_space                   */
+      BOp(ensure_space, ip);
+      {
+	Int sz =  PREG->u.ip.i;   
+	fprintf(stderr,"ensuring %ld\n", sz);
+	PREG = NEXTOP(PREG,ip);
+	if (Unsigned(H) + sz > Unsigned(YREG)-CreepFlag) {
+	  ASP = YREG+E_CB;
+	  if (ASP > (CELL *)PROTECT_FROZEN_B(B))
+	    ASP = (CELL *)PROTECT_FROZEN_B(B);
+	  saveregs();
+	  if (!Yap_gcl(sz, 0, ENV, NEXTOP(PREG,ip))) {
+	    PREG = NEXTOP(PREG,ip);
+	    Yap_Error(OUT_OF_STACK_ERROR,TermNil,Yap_ErrorMessage);
+	    setregs();
+	    FAIL();
+	  } else {
+	    setregs();
+	  }
+	} 
+      }
+      JMPNext();
+      ENDBOp();
+
 /*****************************************************************
 *        try and retry of dynamic predicates                     *
 *****************************************************************/
diff --git a/C/amasm.c b/C/amasm.c
index 35f70b78b..e02bdf653 100755
--- a/C/amasm.c
+++ b/C/amasm.c
@@ -509,6 +509,7 @@ a_cle(op_numbers opcode, yamop *code_p, int pass_no, struct intermediates *cip)
   return code_p;
 }
 
+
 inline static yamop *
 a_e(op_numbers opcode, yamop *code_p, int pass_no)
 {
@@ -1094,6 +1095,21 @@ a_blob(CELL rnd1, op_numbers opcode, int *clause_has_blobsp, yamop *code_p, int
   return code_p;
 }
 
+static yamop *
+a_ensure_space(op_numbers opcode, yamop *code_p, int pass_no, struct intermediates *cip, clause_info *clinfo) 
+{
+  if (cip->cpc->rnd1 > 4096 && FALSE) {
+    if (pass_no) {
+      code_p->opc = emit_op(opcode);
+      code_p->u.ip.i = sizeof(CELL) * cip->cpc->rnd1;
+      code_p->u.ip.p = clinfo->CurrentPred;
+    }
+    GONEXT(ip);
+  }
+  return code_p;
+}
+
+
 inline static yamop *
 a_wdbt(CELL rnd1, op_numbers opcode, int *clause_has_dbtermp, yamop *code_p, int pass_no, struct intermediates *cip)
 {
@@ -3531,6 +3547,9 @@ do_pass(int pass_no, yamop **entry_codep, int assembling, int *clause_has_blobsp
       /* reset dealloc_found in case there was a branch */
       clinfo.dealloc_found = FALSE;
       break;
+    case ensure_space_op:
+      code_p = a_ensure_space(_ensure_space, code_p, pass_no, cip, &clinfo);
+      break;
     case pop_op:
       if (cip->cpc->rnd1 == 1)
 	code_p = a_e(_pop, code_p, pass_no);
diff --git a/C/compiler.c b/C/compiler.c
index 9816daccf..6e49a6e2c 100755
--- a/C/compiler.c
+++ b/C/compiler.c
@@ -201,6 +201,8 @@ typedef struct compiler_struct_struct {
   int onhead;
   int onbranch;
   int curbranch;
+  Int space_used;
+  PInstr *space_op;
   Prop current_p0;
 #ifdef TABLING_INNER_CUTS
   PInstr *cut_mark;
@@ -458,6 +460,7 @@ c_var(Term t, Int argno, unsigned int arity, unsigned int level, compiler_struct
     } else
 #endif
     if (cglobs->onhead) {
+      cglobs->space_used ++;
       if (level == 0)
 	Yap_emit((new ? (++cglobs->nvars, get_var_op) : get_val_op), t, argno, &cglobs->cint);
       else
@@ -725,6 +728,7 @@ c_arg(Int argno, Term t, unsigned int arity, unsigned int level, compiler_struct
 		      : unify_num_op) :
 	    write_num_op), (CELL) t, Zero, &cglobs->cint);
   } else if (IsPairTerm(t)) {
+    cglobs->space_used += 2;
     if (optimizer_on && level < 6) {
 #if !defined(THREADS)
       /* discard code sharing because we cannot write on shared stuff */
@@ -792,6 +796,7 @@ c_arg(Int argno, Term t, unsigned int arity, unsigned int level, compiler_struct
 	return;
       }
     }
+    cglobs->space_used += 1+arity;
     if (level == 0)
       Yap_emit((cglobs->onhead ? get_struct_op : put_struct_op),
 	   (CELL) FunctorOfTerm(t), argno, &cglobs->cint);
@@ -2077,6 +2082,8 @@ c_head(Term t, compiler_struct *cglobs)
   cglobs->onlast = FALSE;
   cglobs->curbranch = cglobs->onbranch = 0;
   cglobs->branch_pointer = cglobs->parent_branches;
+  cglobs->space_used = 0;
+  cglobs->space_op = NULL;
   if (IsAtomTerm(t)) {
     Yap_emit(name_op, (CELL) AtomOfTerm(t), Zero, &cglobs->cint);
 #ifdef BEAM
@@ -2086,6 +2093,8 @@ c_head(Term t, compiler_struct *cglobs)
 #endif
     return;
   }
+  Yap_emit(ensure_space_op, Zero , Zero, &cglobs->cint);
+  cglobs->space_op = cglobs->cint.cpc;
   f = FunctorOfTerm(t);
   Yap_emit(name_op, (CELL) NameOfFunctor(f), ArityOfFunctor(f), &cglobs->cint);
 #ifdef BEAM
@@ -3516,6 +3525,9 @@ Yap_cclause(volatile Term inp_clause, Int NOfArgs, Term mod, volatile Term src)
     c_body(body, mod, &cglobs);
     /* Insert blobs at the very end */ 
 
+    if (cglobs.space_op)
+      cglobs.space_op->rnd1 = cglobs.space_used;
+
     if (cglobs.cint.BlobsStart != NULL) {
       cglobs.cint.cpc->nextInst = cglobs.cint.BlobsStart;
       cglobs.cint.BlobsStart = NULL;
diff --git a/C/computils.c b/C/computils.c
index 25dc70335..b9f2738e9 100755
--- a/C/computils.c
+++ b/C/computils.c
@@ -714,6 +714,7 @@ static char *opformat[] =
   "unify_last_dbterm\t%w",
   "unify_last_longint\t%w",
   "unify_last_bigint\t%l",
+  "ensure_space",
   "native_code",
   "function_to_var\t%v,%B",
   "function_to_val\t%v,%B",
diff --git a/H/YapOpcodes.h b/H/YapOpcodes.h
index 9ab8d22db..9c706e15b 100644
--- a/H/YapOpcodes.h
+++ b/H/YapOpcodes.h
@@ -24,6 +24,7 @@
   OPCODE(alloc_for_logical_pred     ,L),
   OPCODE(copy_idb_term              ,e),
   OPCODE(unify_idb_term             ,e),
+  OPCODE(ensure_space               ,ip),
   OPCODE(spy_or_trymark             ,Otapl),
   OPCODE(try_and_mark               ,Otapl),
   OPCODE(count_retry_and_mark       ,Otapl),
diff --git a/H/amidefs.h b/H/amidefs.h
index 642d192cd..e18e68a40 100644
--- a/H/amidefs.h
+++ b/H/amidefs.h
@@ -477,6 +477,11 @@ typedef struct yami {
       struct yami               *l4;
       CELL next;
     } ollll;
+    struct {
+      Int		  i;
+      struct pred_entry  *p;
+      CELL next;
+    } ip;
     struct {
       struct yami        *l;
       struct pred_entry  *p;
diff --git a/H/compile.h b/H/compile.h
index 706055e08..1b0a0e798 100755
--- a/H/compile.h
+++ b/H/compile.h
@@ -77,6 +77,7 @@ typedef enum compiler_op {
   unify_last_dbterm_op,
   unify_last_longint_op,
   unify_last_bigint_op,
+  ensure_space_op,
   native_op,
   f_var_op,
   f_val_op,
diff --git a/H/findclause.h b/H/findclause.h
index c24138c07..eb8899109 100644
--- a/H/findclause.h
+++ b/H/findclause.h
@@ -289,6 +289,9 @@
     case _write_longint:
       cl = NEXTOP(cl,i);
       break;
+    case _ensure_space:
+      cl = NEXTOP(cl,ip);
+      break;
     case _unify_l_list:
       cl = NEXTOP(cl,o);
       break;
@@ -646,9 +649,6 @@
     case _write_x_loc:
       cl = NEXTOP(cl,x);
       break;
-    case _write_x_val:
-      cl = NEXTOP(cl,x);
-      break;
     case _write_x_var:
       if (!(nofregs = delete_regcopy(myregs, nofregs, cl->u.x.x))) {
 	clause->Tag = (CELL)NULL;
diff --git a/H/rclause.h b/H/rclause.h
index f7715c73d..5acb6dfc0 100644
--- a/H/rclause.h
+++ b/H/rclause.h
@@ -240,6 +240,12 @@ restore_opcodes(yamop *pc, yamop *max)
       IntegerInCodeAdjust(pc->u.i.i);
       pc = NEXTOP(pc,i);
       break;
+      /* instructions type ip */
+    case _ensure_space:
+      IntegerInCodeAdjust(pc->u.ip.i);
+      pc->u.ip.p = PtoPredAdjust(pc->u.ip.p);
+      pc = NEXTOP(pc,ip);
+      break;
       /* instructions type l */
     case _Ystop:
     case _jump:
diff --git a/H/walkclause.h b/H/walkclause.h
index 539db02f2..f174a3fc1 100644
--- a/H/walkclause.h
+++ b/H/walkclause.h
@@ -184,6 +184,10 @@
     case _write_longint:
       pc = NEXTOP(pc,i);
       break;
+      /* instructions type ip */
+    case _ensure_space:
+      pc = NEXTOP(pc,ip);
+      break;
       /* instructions type l */
     case _Ystop:
       return found_ystop(pc, clause_code, startp, endp, pp);
diff --git a/misc/buildops b/misc/buildops
index 719bd1081..3906566ff 100644
--- a/misc/buildops
+++ b/misc/buildops
@@ -822,7 +822,7 @@ opinfo("p_nonvar_x",[body,ifthenelse]).
 opinfo("p_nonvar_y",[body,ifthenelse]).
 opinfo("save_b_x",[body,new("x")]).
 opinfo("save_b_y",[body,new("y")]).
-opinfo("write_x_val",[body]).
+opinfo("ensure_space",[body]).
 opinfo("write_x_loc",[body]).
 opinfo("write_x_var",[body,new("x")]).
 opinfo("write_y_var",[body,new("y")]).
diff --git a/packages/semweb/Makefile.in b/packages/semweb/Makefile.in
index 056d5bb73..ce6e49a36 100755
--- a/packages/semweb/Makefile.in
+++ b/packages/semweb/Makefile.in
@@ -50,7 +50,7 @@ LD=@DO_SECOND_LD@	@SHLIB_LD@
 LDFLAGS=@EXTRA_LIBS_FOR_SWIDLLS@
 
 BINTARGET=$(DESTDIR)$(YAPLIBDIR)
-PLTARGET=$(DESTDIR)$(SHAREDIR)/http
+PLTARGET=$(DESTDIR)$(SHAREDIR)/semweb
 
 FINAL_BINTARGET=$(YAPLIBDIR)
 FINAL_PLTARGET=$(SHAREDIR)
@@ -117,6 +117,7 @@ install:	$(TARGETS) $(LIBPL)
 		for f in $(TARGETS); do \
 		  $(INSTALL) -m 755 $$f $(BINTARGET); \
 		done
+		mkdir -p $(PLTARGET)
 		for f in $(DATA) $(LIBPL) $(srcdir)/README; do \
 		  $(INSTALL_DATA) $$f $(PLTARGET); \
 		done
diff --git a/packages/zlib/test_zlib.pl b/packages/zlib/test_zlib.pl
index 88d7536e7..b9e6b6943 100644
--- a/packages/zlib/test_zlib.pl
+++ b/packages/zlib/test_zlib.pl
@@ -13,10 +13,6 @@
 :- use_module(library(socket)).
 :- use_module(library(debug)).
 
-:- expects_dialect(swi).
-:- assert(system:swi_io).
-
-
 test_zlib :-
 	run_tests([ zlib
 		  ]).
@@ -31,7 +27,7 @@ test(gunzip,
      ]) :-
 	gzopen('plunit-tmp.gz', read, ZIn),
 	call_cleanup(read_stream_to_codes(ZIn, Codes0), close(ZIn)),
-	myread_file_to_codes('test_zlib.pl', Codes1),
+	read_file_to_codes('test_zlib.pl', Codes1),
 	Codes0 == Codes1.
 
 %	gzip: Can gunzip read our compressed file
@@ -39,11 +35,11 @@ test(gunzip,
 test(gzip,
      [ cleanup(delete_file('plunit-tmp.gz'))
      ]) :-
-	myread_file_to_codes('test_zlib.pl', Codes),
+	read_file_to_codes('test_zlib.pl', Codes),
 	gzopen('plunit-tmp.gz', write, ZOut),
 	format(ZOut, '~s', [Codes]),
 	close(ZOut),
-	myread_file_to_codes(pipe('gunzip < plunit-tmp.gz'), Codes1),
+	read_file_to_codes(pipe('gunzip < plunit-tmp.gz'), Codes1),
 	Codes == Codes1.
 
 %	deflate: test read/write of deflate format
@@ -51,7 +47,7 @@ test(gzip,
 test(deflate,
      [ cleanup(delete_file('plunit-tmp.z'))
      ]) :-
-	myread_file_to_codes('test_zlib.pl', Codes),
+	read_file_to_codes('test_zlib.pl', Codes),
 	open('plunit-tmp.z', write, Out),
 	zopen(Out, ZOut, []),
 	format(ZOut, '~s', [Codes]),
@@ -202,9 +198,7 @@ get_data(ZIn, N) :-
 		 *	       UTIL		*
 		 *******************************/
 
-myread_file_to_codes(File, Codes) :-
+read_file_to_codes(File, Codes) :-
 	open(File, read, In),
 	call_cleanup(read_stream_to_codes(In, Codes), close(In)).
 
-:- retract(system:swi_io).
-