1 files changed, 1 insertions, 1 deletions
diff --git a/lib/axlsx.rb b/lib/axlsx.rb
index 46d1c9bf..6fce32b5 100644
--- a/lib/axlsx.rb
+++ b/lib/axlsx.rb
@@ -71,7 +71,7 @@ module Axlsx
     chars = []
     while index >= 26 do
       chars << ((index % 26) + 65).chr
-      index = index / 26 - 1
+      index = (index / 26).to_i - 1
     end
     chars << (index + 65).chr
     chars.reverse.join