diff --git a/library/lammpi/CMakeLists.txt b/library/lammpi/CMakeLists.txt
index ff6a134a8..80f0ac643 100644
--- a/library/lammpi/CMakeLists.txt
+++ b/library/lammpi/CMakeLists.txt
@@ -2,7 +2,7 @@
 set (MPI_SOURCES
   hash.c prologterms2c.c yap_mpi.c)
 
-  macro_optional_find_package(MPI ON)
+  macro_optional_find_package(Mpi ON)
   macro_log_feature (MPI_C_FOUND "Mpi"
     "Use Mpi System"
     "http://www.mpi.org" FALSE)
diff --git a/pl/debug.yap b/pl/debug.yap
index 66b78a5a9..14568b36d 100644
--- a/pl/debug.yap
+++ b/pl/debug.yap
@@ -307,6 +307,7 @@ be lost.
 %'$do_spy'(V, M, CP, Flag) :-
 %	writeln('$do_spy'(V, M, CP, Flag)), fail.
 '$do_spy'(V, M, CP, Flag) :-
+    '$stop_creeping',
 	var(V), !,
 	'$do_spy'(call(V), M, CP, Flag).
 '$do_spy'(!, _, CP, _) :-
@@ -323,6 +324,7 @@ be lost.
 '$do_spy'((T->A;B), M, CP, CalledFromDebugger) :- !,
 	( '$do_spy'(T, M, CP, debugger) -> '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
+      
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((T->A|B), M, CP, CalledFromDebugger) :- !,
@@ -331,6 +333,7 @@ be lost.
 	->
 	  '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
+     '$stop_creeping',
 	  '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((T->A), M, CP, CalledFromDebugger) :- !,
@@ -339,13 +342,15 @@ be lost.
 	(
 	  '$do_spy'(A, M, CP, CalledFromDebugger)
 	;
-	  '$do_spy'(B, M, CP, CalledFromDebugger)
+     '$stop_creeping',
+     '$do_spy'(B, M, CP, CalledFromDebugger)
 	).
 '$do_spy'((A|B), M, CP, CalledFromDebugger) :- !,
 	(
 	  '$do_spy'(A, M, CP, CalledFromDebugger )
 	;
-	  '$do_spy'(B, M, CP, CalledFromDebugger )
+     '$stop_creeping',
+     '$do_spy'(B, M, CP, CalledFromDebugger )
 	).
 '$do_spy'((\+G), M, CP, CalledFromDebugger) :- !,
 	\+ '$do_spy'(G, M, CP, CalledFromDebugger).
@@ -427,44 +432,44 @@ be lost.
 	    /* go execute the continuation	*/
 	    (
 	       /* exit port */
-	       Retry = false,
-	       /* found an answer, so it can redo */
-	       nb_setarg(6, Info, true),
-	      '$show_trace'(exit,G,Module,GoalNumber,Det),	/* output message at exit	*/
-	       /* exit port */
-	       /* get rid of deterministic computations */
-	      (
-		Det == true
+         Retry = false,
+         /* found an answer, so it can redo */
+         nb_setarg(6, Info, true),
+         '$show_trace'(exit,G,Module,GoalNumber,Det),	/* output message at exit	*/
+        /* exit port */
+        /* get rid of deterministic computations */
+        (
+         Det == true
 		->
-		'$$cut_by'(CP)
+         '$$cut_by'(CP)
 		;
-		true
-	      ),
-	      '$continue_debugging'(exit, CalledFromDebugger)
+         true
+        ),
+         '$continue_debugging'(exit, CalledFromDebugger)
 	     ;
-	       % make sure we are in system mode when running the debugger.
-		/* backtracking from exit				*/
-	        /* we get here when we want to redo a goal		*/
-		/* redo port */
-	      (
-	         arg(6, Info, true)
-	      ->
-	       '$stop_creeping',
-	        '$show_trace'(redo,G,Module,GoalNumber,_), /* inform user_error		*/
-	        nb_setarg(6, Info, false)
-	       ;
-	         true
-	      ),
+	     /* make sure we are in system mode when running the debugger. */
+         /* backtracking from exit				*/
+         /* we get here when we want to redo a goal		*/
+         /* redo port */
+         (
+          arg(6, Info, true)
+         ->
+          '$stop_creeping',
+          '$show_trace'(redo,G,Module,GoalNumber,_), /* inform user_error		*/
+         nb_setarg(6, Info, false)
+         ;
+          true
+         ),
 	     '$continue_debugging'(fail, CalledFromDebugger),
-	     fail			/* to backtrack to spycalls	*/
-	     )
+	     fail			/* to backtrack to spycall	*/
+        )
 	  ;
-         '$stop_creeping',
+        '$stop_creeping',
 	    '$show_trace'(fail,G,Module,GoalNumber,_), /* inform at fail port		*/
-	    '$continue_debugging'(fail, CalledFromDebugger),
+       '$continue_debugging'(fail, CalledFromDebugger),
 	    /* fail port */
 	    fail
-	).
+       ).
 
 '$enter_goal'(GoalNumber, G, Module) :-
     '$zip'(GoalNumber, G, Module), !.
@@ -512,7 +517,7 @@ be lost.
 	),
 	'$execute_nonstop'(G1,M).
 '$spycall'(G, M, _, _) :-
-        (
+    (
 	 '$system_predicate'(G,M)
 	;
 	 '$system_module'(M)
@@ -572,6 +577,7 @@ be lost.
 	 (CP1 == CP2 -> ! ; ( true ; '$creep', fail ) ),
 	  '$stop_creeping'
 	;
+     '$stop_creeping',
 	 fail
 	).
 '$creep'(G,M) :-
diff --git a/pl/os.yap b/pl/os.yap
index d1a634913..65277490c 100644
--- a/pl/os.yap
+++ b/pl/os.yap
@@ -143,7 +143,7 @@ Execute a new shell.
 unix(V) :- var(V), !,
 	'$do_error'(instantiation_error,unix(V)).
 unix(argv(L)) :-
-	prolog_flag(argv, L).
+	current_prolog_flag(argv, L).
 unix(cd) :- cd('~').
 unix(cd(A)) :- cd(A).
 unix(environ(X,Y)) :- '$do_environ'(X,Y).
diff --git a/pl/preds.yap b/pl/preds.yap
index abef37fb1..51e960537 100644
--- a/pl/preds.yap
+++ b/pl/preds.yap
@@ -655,25 +655,49 @@ is the atom  _A_.
 */
 system_predicate(A,T1) :-
 	'$yap_strip_module'( T1, M, T),
+    '$system_predicate3'( A, M, T).
+
+'$system_predicate3'( A, M, T) :-
 	(
 	 M \= prolog,
-	 '$current_predicate'(A, M, T0, system)
+	 '$current_predicate'(A, M, T, system)
 	 ;
 	 '$imported_predicate'(T, M, SourceT, SourceMod),
 	 M \= prolog,
 	 functor(T, A, _),
 	 '$system_predicate'(SourceT, SourceMod)
 	;
-	 '$current_predicate'(A, prolog, T0, system)
+	 '$current_predicate'(A, prolog, T, system)
 	).
 
 /** @pred  system_predicate( ?_P_ )
 
-Defines the relation:  _P_ is a currently defined system predicate.
+Defines the relation:  indicator _P_ refers to a currently defined system predicate.
 */
 system_predicate(P0) :-
 	strip_module(P0, M, P),
-	system_predicate(_, M:P).
+
+    (
+     var(P)
+    ->
+     P = A/Arity,
+     '$system_predicate3'( A, M, T),
+     functor(T, A, Arity)
+    ;
+     P = A//Arity2
+    ->
+     '$system_predicate3'( A, M, T),
+     functor(T, A, Arity),
+     Arity2 is Arity+2
+    ;
+     P = A/Arity
+    ->
+     '$system_predicate3'( A, M, T),
+     functor(T, A, Arity)
+    ;
+    '$do_error'(type_error(predicate_indicator,P),
+                system_predicate(P0))
+    ).
 
 
 /**