diff --git a/components/synedit/synedithighlighterfoldbase.pas b/components/synedit/synedithighlighterfoldbase.pas
index e22254e299..3849e7197b 100644
--- a/components/synedit/synedithighlighterfoldbase.pas
+++ b/components/synedit/synedithighlighterfoldbase.pas
@@ -805,7 +805,7 @@ var
   r: Pointer;
 begin
   Assert(CurrentRanges <> nil, 'TSynCustomFoldHighlighter.FoldBlockEndLevel requires CurrentRanges');
-  if (ALineIndex < 0) or (ALineIndex >= CurrentLines.Count) then
+  if (ALineIndex < 0) or (ALineIndex >= CurrentLines.Count - 1) then
     exit(0);
   r := CurrentRanges[ALineIndex];
   if (r <> nil) and (r <> NullRange) then
@@ -820,7 +820,7 @@ var
   r: Pointer;
 begin
   Assert(CurrentRanges <> nil, 'TSynCustomFoldHighlighter.FoldBlockMinLevelrequires CurrentRanges');
-  if (ALineIndex < 0) or (ALineIndex >= CurrentLines.Count) then
+  if (ALineIndex < 0) or (ALineIndex >= CurrentLines.Count - 1) then
     exit(0);
   r := CurrentRanges[ALineIndex];
   if (r <> nil) and (r <> NullRange) then
diff --git a/components/synedit/test/testhighlightfoldbase.pas b/components/synedit/test/testhighlightfoldbase.pas
index 35d6518fee..cf79c13de8 100644
--- a/components/synedit/test/testhighlightfoldbase.pas
+++ b/components/synedit/test/testhighlightfoldbase.pas
@@ -12,6 +12,15 @@ type
 
   // used by Fold / MarkupWord
 
+  TTestExpValuesForLine = record
+    Line: integer;
+    Exp: Array of integer;
+  end;
+
+  function ExpVLine(ALine: Integer; AExp: Array of integer): TTestExpValuesForLine;
+
+type
+
   { TTestBaseHighlighterPas }
 
   { TTestBaseHighlighterFoldBase }
@@ -25,6 +34,9 @@ type
     procedure ReCreateEdit; reintroduce;
 
     procedure CheckFoldOpenCounts(Name: String; Expected: Array of Integer);
+    procedure CheckFoldLengths(Name: String; Expected: Array of TTestExpValuesForLine);
+    procedure CheckFoldEndLines(Name: String; Expected: Array of TTestExpValuesForLine);
+
     procedure CheckFoldInfoCounts(Name: String; Filter: TSynFoldActions; Expected: Array of Integer);
     procedure CheckFoldInfoCounts(Name: String; Filter: TSynFoldActions; Group: Integer; Expected: Array of Integer);
 
@@ -34,6 +46,16 @@ type
 
 implementation
 
+function ExpVLine(ALine: Integer; AExp: array of integer): TTestExpValuesForLine;
+var
+  i: Integer;
+begin
+  Result.Line := ALine;
+  SetLength(Result.Exp, Length(AExp));
+  for i := low(AExp) to high(AExp) do
+    Result.Exp[i] := AExp[i];
+end;
+
 { TTestBaseHighlighterFoldBase }
 
 procedure TTestBaseHighlighterFoldBase.SetUp;
@@ -72,6 +94,28 @@ begin
     AssertEquals(Name + 'OpenCount Line='+IntToStr(i),  Expected[i], FTheHighLighter.FoldBlockOpeningCount(i));
 end;
 
+procedure TTestBaseHighlighterFoldBase.CheckFoldLengths(Name: String;
+  Expected: array of TTestExpValuesForLine);
+var
+  i, j: Integer;
+begin
+  for i := 0 to high(Expected) do
+    for j := 0 to high(Expected[i].Exp) do
+      AssertEquals(Name + 'FoldLength Line='+IntToStr(Expected[i].Line) + ' idx='+IntToStr(j),
+        Expected[i].Exp[j], FTheHighLighter.FoldLineLength(Expected[i].Line, j));
+end;
+
+procedure TTestBaseHighlighterFoldBase.CheckFoldEndLines(Name: String;
+  Expected: array of TTestExpValuesForLine);
+var
+  i, j: Integer;
+begin
+  for i := 0 to high(Expected) do
+    for j := 0 to high(Expected[i].Exp) do
+      AssertEquals(Name + 'FoldEnd Line='+IntToStr(Expected[i].Line) + ' idx='+IntToStr(j),
+        Expected[i].Exp[j], FTheHighLighter.FoldEndLine(Expected[i].Line, j));
+end;
+
 procedure TTestBaseHighlighterFoldBase.CheckFoldInfoCounts(Name: String;
   Filter: TSynFoldActions; Expected: array of Integer);
 begin
diff --git a/components/synedit/test/testhighlightxml.pas b/components/synedit/test/testhighlightxml.pas
index 7c2c704746..091e9b6576 100644
--- a/components/synedit/test/testhighlightxml.pas
+++ b/components/synedit/test/testhighlightxml.pas
@@ -5,19 +5,27 @@ unit TestHighlightXml;
 interface
 
 uses
-  Classes, SysUtils, fpcunit, testregistry, TestBase, SynHighlighterXML;
+  Classes, SysUtils, fpcunit, testregistry, TestBase, TestHighlightFoldBase, SynHighlighterXML,
+  SynEditHighlighterFoldBase;
 
 type
 
   { THighlightXml }
 
-  THighlightXml = class(TTestBase)
+  THighlightXml = class(TTestBaseHighlighterFoldBase)
+  protected
+    function CreateTheHighLighter: TSynCustomFoldHighlighter; override;
   published
     procedure TestXml;
   end; 
 
 implementation
 
+function THighlightXml.CreateTheHighLighter: TSynCustomFoldHighlighter;
+begin
+  Result := TSynXMLSyn.Create(nil);
+end;
+
 procedure THighlightXml.TestXml;
   function TestText: TStringArray;
   begin
@@ -31,12 +39,35 @@ var
   hl: TSynXMLSyn;
 begin
   ReCreateEdit;
-  hl := TSynXMLSyn.Create(nil);
-  SynEdit.Highlighter := hl;
   SetLines(TestText);
 
-  SynEdit.Highlighter := nil;
-  hl.free;
+  CheckFoldOpenCounts('simple', [1,0,0]);
+  CheckFoldLengths   ('simple', [ExpVLine(0,[2])]);
+  CheckFoldEndLines  ('simple', [ExpVLine(0,[2])]);
+
+  SetLines(['<a>', '<b><c>', '</c>', '', '</b></a>', '']);
+  CheckFoldOpenCounts('nested', [1,2,0,0,0]);
+  CheckFoldLengths   ('nested', [ExpVLine(0, [4]),  ExpVLine(1, [3,1]) ]);
+  CheckFoldEndLines  ('nested', [ExpVLine(0, [4]),  ExpVLine(1, [4,2]) ]);
+
+  // c is not closed, and ended by b
+  SetLines(['<a>', '<b><c>', '', '', '</b></a>', '']);
+  CheckFoldOpenCounts('bad nested', [1,2,0,0,0]);
+  CheckFoldLengths   ('bad nested', [ExpVLine(0, [4]),  ExpVLine(1, [3,3]) ]);
+  CheckFoldEndLines  ('bad nested', [ExpVLine(0, [4]),  ExpVLine(1, [4,4]) ]);
+
+  // a is not closed
+  SetLines(['<a>', '<b><c>', '</c>', '', '</b>', '']);
+  CheckFoldOpenCounts('open end', [1,2,0,0,0]);
+  CheckFoldLengths   ('open end', [ExpVLine(0, [4]),  ExpVLine(1, [3,1]) ]);
+  CheckFoldEndLines  ('open end', [ExpVLine(0, [4]),  ExpVLine(1, [4,2]) ]);
+
+  // a is not closed
+  SetLines(['<a>', '']);
+  CheckFoldOpenCounts('open end (one line)', [0]);
+  //CheckFoldLengths   ('open end (one line)', [ExpVLine(0, [0]) ]);
+  //CheckFoldEndLines  ('open end (one line)', [ExpVLine(0, [0]) ]);
+
 end;