Worksheet#merge_cells sometimes produced invalid merge ranges when given an array of cells.

Merging e.g. cells A9 and A10 resulted in invalid range "A10:A9".

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/axlsx/workbook/worksheet/worksheet.rb b/lib/axlsx/workbook/worksheet/worksheet.rb
index 2205b97d..887968e0 100644
--- a/lib/axlsx/workbook/worksheet/worksheet.rb
+++ b/lib/axlsx/workbook/worksheet/worksheet.rb
@@ -204,7 +204,7 @@ module Axlsx
       @merged_cells << if cells.is_a?(String)
                          cells
                        elsif cells.is_a?(Array)
-                         cells = cells.sort { |x, y| x.r <=> y.r }
+                         cells = cells.sort { |x, y| [x.index, x.row.index] <=> [y.index, y.row.index] }
                          "#{cells.first.r}:#{cells.last.r}"
                        end
     end