lib/write_xlsx/chart/series.rb in write_xlsx-1.09.3 vs lib/write_xlsx/chart/series.rb in write_xlsx-1.09.4

@@ -345,10 +345,10 @@
             end
 
             property = label.dup
 
             # Convert formula.
-            if property[:value] && property[:value] =~ /^=[^!]+!\$/
+            if property[:value] && property[:value].to_s =~ /^=[^!]+!\$/
               property[:formula] = property[:value]
             end
 
             if property[:formula]
               property[:formula] = property[:formula].sub(/^=/, '')