diff --git a/components/synedit/synedittextbuffer.pp b/components/synedit/synedittextbuffer.pp
index 0665c1f395..2f56753b73 100644
--- a/components/synedit/synedittextbuffer.pp
+++ b/components/synedit/synedittextbuffer.pp
@@ -869,14 +869,15 @@ end;
 function TSynEditStringList.LogicPosIsCombining(const AChar: PChar): Boolean;
 begin
   Result := (
-     ( (AChar[0] = #$CC) {and (AChar[1] in [#$80..#$FF])} ) or  // Combining Diacritical Marks (belongs to previos char) 0300-036F
-     ( (AChar[0] = #$CD) and (AChar[1] in [#$80..#$AF]) ) or  // Combining Diacritical Marks
-     ( (AChar[0] = #$E1) and (AChar[1] = #$B7) ) or           // Combining Diacritical Marks Supplement 1DC0-1DFF
-                                    // (AChar[0+2] in [#$80..#$BF])
-     ( (AChar[0] = #$E2) and (AChar[1] = #$83) and
-       (AChar[2] in [#$90..#$FF]) ) or                                  // Combining Diacritical Marks for Symbols 20D0-20FF
-     ( (AChar[0] = #$EF) and (AChar[1] = #$B8) and
-       (AChar[2] in [#$A0..#$AF]) )                                     // Combining half Marks FE20-FE2F
+   ( (AChar[0] = #$CC) ) or                                                       // Combining Diacritical Marks (belongs to previos char) 0300-036F
+   ( (AChar[0] = #$CD) and (AChar[1] in [#$80..#$AF]) ) or                        // Combining Diacritical Marks
+   ( (AChar[0] = #$D8) and (AChar[1] in [#$90..#$9A]) ) or                        // Arabic 0610 (d890)..061A (d89a)
+   ( (AChar[0] = #$D9) and (AChar[1] in [#$8b..#$9f, #$B0]) ) or                  // Arabic 064B (d98b)..065F (d99f) // 0670 (d9b0)
+   ( (AChar[0] = #$DB) and (AChar[1] in [#$96..#$9C, #$9F..#$A4, #$A7..#$A8, #$AA..#$AD]) ) or // Arabic 06D6 (db96)..  .. ..06EA (dbaa)
+   ( (AChar[0] = #$E0) and (AChar[1] = #$A3) and (AChar[2] in [#$A4..#$BE]) ) or  // Arabic 08E4 (e0a3a4) ..08FE (e0a3be)
+   ( (AChar[0] = #$E1) and (AChar[1] = #$B7) ) or                                 // Combining Diacritical Marks Supplement 1DC0-1DFF
+   ( (AChar[0] = #$E2) and (AChar[1] = #$83) and (AChar[2] in [#$90..#$FF]) ) or  // Combining Diacritical Marks for Symbols 20D0-20FF
+   ( (AChar[0] = #$EF) and (AChar[1] = #$B8) and (AChar[2] in [#$A0..#$AF]) )     // Combining half Marks FE20-FE2F
   );
 end;