diff --git a/src/fosslight_util/write_excel.py b/src/fosslight_util/write_excel.py
index 24e60b0..618cc0c 100755
--- a/src/fosslight_util/write_excel.py
+++ b/src/fosslight_util/write_excel.py
@@ -215,10 +215,11 @@ def write_result_to_sheet(worksheet, sheet_contents):
     for row_item in sheet_contents:
         worksheet.write(row, 0, row)
         for col_num, value in enumerate(row_item):
+            value = "" if value is None else str(value)
             if len(value) > MAX_EXCEL_URL_LENGTH and (value.startswith("http://") or value.startswith("https://")):
-                worksheet.write_string(row, col_num + 1, str(value))
+                worksheet.write_string(row, col_num + 1, value)
             else:
-                worksheet.write(row, col_num + 1, str(value))
+                worksheet.write(row, col_num + 1, value)
         row += 1