diff --git a/components/synedit/synedit.pp b/components/synedit/synedit.pp
index 38557b2bcc..76ffa4e2d6 100644
--- a/components/synedit/synedit.pp
+++ b/components/synedit/synedit.pp
@@ -7817,8 +7817,12 @@ begin
                 //utf8bidi.insert(Temp,AChar,CaretNew.X);
                 CaretX := CaretNew.X;
                 {$ELSE}
-                Temp:=copy(Temp,1,LogCaretXY.X-1)+AChar
-                     +copy(Temp,LogCaretXY.X+Counter,length(Temp));
+                Len := Length(Temp);
+                if LogCaretXY.X<=Len then
+                  Temp:=copy(Temp,1,LogCaretXY.X-1)+AChar
+                       +copy(Temp,LogCaretXY.X+Counter,length(Temp))
+                else
+                  Temp:=Temp+StringOfChar(' ', LogCaretXY.X-1-Len)+AChar;
                 {$ENDIF}
                 CaretNew := Point((CaretX + 1), CaretY);
                 TrimmedSetLine(CaretY - 1, Temp);
diff --git a/lcl/include/control.inc b/lcl/include/control.inc
index 1ae825dd6c..98fec5f244 100644
--- a/lcl/include/control.inc
+++ b/lcl/include/control.inc
@@ -1892,7 +1892,9 @@ end;
 {------------------------------------------------------------------------------
   function TControl.AutoSizeCanStart: boolean;
   
-  Returns true if DoAutoSize can start.
+  Returns true if DoAutoSize can start. That means, it tests the minimum
+  requirements to start. Some controls need even more.
+
   It returns false if
   - AutoSize=false
   - or the control is currently autosizing