diff --git a/check/fixes.frm b/check/fixes.frm
index 48e5ec8d..8829ae83 100644
--- a/check/fixes.frm
+++ b/check/fixes.frm
@@ -4525,6 +4525,123 @@ assert stdout =~ exact_pattern(<<'EOF')
 sumpow: 129
 EOF
 *--#] Issue796c : 
+*--#[ Issue856 : 
+#-
+Off Statistics;
+CFunction f,g,h;
+
+#define MODE "1"
+#define MAX "4"
+
+* Each expression is a different size:
+#do i = 1,`MAX'
+	Local test`i' = f(`i')^`i';
+	Local htest`i' = g(`i')^{`i'+`MAX'};
+	Local ihtest`i' = h(`i')^{`i'+2*`MAX'};
+#enddo
+.sort
+
+* Start with "htest" expr hidden
+Hide htest1,...,htest`MAX';
+.sort
+
+#do i = 1,`MAX'
+	UnHide htest`i';
+	.sort
+	IntoHide ihtest`i';
+	#if `MODE' == 1
+		InParallel;
+	#endif
+	Multiply 2;
+	.sort
+	Hide htest`i';
+#enddo
+.sort
+
+* UnHide all, mixture of InParallel and regular:
+InParallel htest1,...,htest`MAX';
+UnHide;
+.sort
+
+
+* Reset
+Hide htest1,...,htest`MAX';
+.sort
+
+* Same again, with UnHide in the inparallel module
+#do i = 1,`MAX'
+	UnHide htest`i';
+	IntoHide ihtest`i';
+	#if `MODE' == 1
+		InParallel;
+	#endif
+	Multiply 2;
+	.sort
+	Hide htest`i';
+#enddo
+.sort
+
+UnHide;
+.sort
+
+
+* Reset
+Hide htest1,...,htest`MAX';
+.sort
+
+* Same again, leave the first expression in the Hide file
+#do i = 2,`MAX'
+	UnHide htest`i';
+	.sort
+	IntoHide ihtest`i';
+	#if `MODE' == 1
+		InParallel;
+	#endif
+	Multiply 2;
+	.sort
+	Hide htest`i';
+#enddo
+.sort
+
+UnHide;
+.sort
+
+
+* Reset
+Hide htest1,...,htest`MAX';
+.sort
+
+* Same again, leave the first expression in the Hide file, but take from the end
+#do i = `MAX',2,-1
+	UnHide htest`i';
+	.sort
+	IntoHide ihtest`i';
+	#if `MODE' == 1
+		InParallel;
+	#endif
+	Multiply 2;
+	.sort
+	Hide htest`i';
+#enddo
+.sort
+
+UnHide;
+Print;
+.end
+assert succeeded?
+assert result("test1") =~ expr("16384*f(1)")
+assert result("htest1") =~ expr("4*g(1)^5")
+assert result("ihtest1") =~ expr("256*h(1)^9")
+assert result("test2") =~ expr("16384*f(2)^2")
+assert result("htest2") =~ expr("16*g(2)^6")
+assert result("ihtest2") =~ expr("256*h(2)^10")
+assert result("test3") =~ expr("16384*f(3)^3")
+assert result("htest3") =~ expr("16*g(3)^7")
+assert result("ihtest3") =~ expr("1024*h(3)^11")
+assert result("test4") =~ expr("16384*f(4)^4")
+assert result("htest4") =~ expr("16*g(4)^8")
+assert result("ihtest4") =~ expr("4096*h(4)^12")
+*--#] Issue856 : 
 *--#[ PullReq535 :
 * This test requires more than the specified 50K workspace.
 #:maxtermsize 200
diff --git a/sources/proces.c b/sources/proces.c
index 06df6280..7fe368f8 100644
--- a/sources/proces.c
+++ b/sources/proces.c
@@ -111,6 +111,9 @@ int Processor(void)
 	AN.PolyFunTodo = 0;
 #ifdef HIDEDEBUG
 	MesPrint("Status at the start of Processor (HideLevel = %d)",AC.HideLevel);
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.infile->name   ,AR.infile->POfill  -AR.infile->PObuffer  ,AR.infile->POfull  -AR.infile->PObuffer  ,AR.infile->POsize/sizeof(WORD)  );
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.outfile->name  ,AR.outfile->POfill -AR.outfile->PObuffer ,AR.outfile->POfull -AR.outfile->PObuffer ,AR.outfile->POsize/sizeof(WORD) );
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.hidefile->name ,AR.hidefile->POfill-AR.hidefile->PObuffer,AR.hidefile->POfull-AR.hidefile->PObuffer,AR.hidefile->POsize/sizeof(WORD));
 	for ( i = 0; i < NumExpressions; i++ ) {
 		e = Expressions+i;
 		ExprStatus(e);
@@ -644,6 +647,9 @@ commonread:;
 	AT.WorkPointer = term;
 #ifdef HIDEDEBUG
 	MesPrint("Status at the end of Processor (HideLevel = %d)",AC.HideLevel);
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.infile->name   ,AR.infile->POfill  -AR.infile->PObuffer  ,AR.infile->POfull  -AR.infile->PObuffer  ,AR.infile->POsize/sizeof(WORD)  );
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.outfile->name  ,AR.outfile->POfill -AR.outfile->PObuffer ,AR.outfile->POfull -AR.outfile->PObuffer ,AR.outfile->POsize/sizeof(WORD) );
+	MesPrint("File %s POfill %l POfull %l POsize %l", AR.hidefile->name ,AR.hidefile->POfill-AR.hidefile->PObuffer,AR.hidefile->POfull-AR.hidefile->PObuffer,AR.hidefile->POsize/sizeof(WORD));
 	for ( i = 0; i < NumExpressions; i++ ) {
 		e = Expressions+i;
 		ExprStatus(e);
diff --git a/sources/store.c b/sources/store.c
index 22205611..b2b1db8c 100644
--- a/sources/store.c
+++ b/sources/store.c
@@ -119,8 +119,8 @@ void SetScratch(FILEHANDLE *f, POSITION *position)
 	if ( f == AR.hidefile ) whichInInBuf = &(AR.InHiBuf);
 	else                    whichInInBuf = &(AR.InInBuf);
 #ifdef HIDEDEBUG
-	if ( f == AR.hidefile ) MesPrint("In the hide file");
-	else MesPrint("In the input file");
+	if ( f == AR.hidefile ) MesPrint("In the hide file: %s", f->name);
+	else MesPrint("In the input file: %s", f->name);
 	MesPrint("SetScratch to position %15p",position);
 	MesPrint("POposition = %15p, full = %l, fill = %l"
 		,&(f->POposition),(f->POfull-f->PObuffer)*sizeof(WORD)
diff --git a/sources/threads.c b/sources/threads.c
index ebf7c8fd..13ebe463 100644
--- a/sources/threads.c
+++ b/sources/threads.c
@@ -1785,7 +1785,6 @@ bucketstolen:;
 					goto ProcErr;
 				}
 				AB[0]->R.outfile = oldoutfile;
-				AB[0]->R.hidefile->POfull = AB[0]->R.hidefile->POfill;
 				AB[0]->R.expflags = AR.expflags;
 				UNLOCK(AS.outputslock);