diff --git a/comparexlsxlsx.go b/comparexlsxlsx.go
new file mode 100644
index 0000000..080f50a
--- /dev/null
+++ b/comparexlsxlsx.go
@@ -0,0 +1,40 @@
+package xls
+
+import (
+	"fmt"
+	"github.com/tealeg/xlsx"
+	"path"
+)
+
+//Compares xls and xlsx files
+func compareXlsXlsx(filepathname string) string {
+	xlsFile, err := Open(path.Join("testdata", filepathname)+".xls", "utf-8")
+	if err != nil {
+		return fmt.Sprintf("Cant open xls file: %s", err)
+	}
+
+	xlsxFile, err := xlsx.OpenFile(path.Join("testdata", filepathname) + ".xlsx")
+	if err != nil {
+		return fmt.Sprintf("Cant open xlsx file: %s", err)
+	}
+
+	for sheet, xlsxSheet := range xlsxFile.Sheets {
+		xlsSheet := xlsFile.GetSheet(sheet)
+		if xlsSheet == nil {
+			return fmt.Sprintf("Cant get xls sheet")
+		}
+		for row, xlsxRow := range xlsxSheet.Rows {
+			xlsRow := xlsSheet.Row(row)
+			for cell, xlsxCell := range xlsxRow.Cells {
+				xlsText := xlsRow.Col(cell)
+				xlsxText := xlsxCell.String()
+				if xlsText != xlsxText {
+					return fmt.Sprintf("Sheet: %d, row: %d, col: %d, xlsx: (%s)[%d], xls: (%s)[%d].",
+						sheet, row, cell, xlsxText, len(xlsxText), xlsText, len(xlsText))
+				}
+			}
+		}
+	}
+
+	return ""
+}
diff --git a/issue47_test.go b/issue47_test.go
new file mode 100644
index 0000000..ab5a713
--- /dev/null
+++ b/issue47_test.go
@@ -0,0 +1,14 @@
+package xls
+
+import (
+	"testing"
+)
+
+func TestIssue47(t *testing.T) {
+	e := compareXlsXlsx("issue47")
+
+	if e != "" {
+		t.Fatalf("XLS an XLSX are not equal: %s", e)
+	}
+
+}
diff --git a/testdata/bigtable.xls b/testdata/bigtable.xls
new file mode 100644
index 0000000..e7c7481
Binary files /dev/null and b/testdata/bigtable.xls differ
diff --git a/testdata/bigtable.xlsx b/testdata/bigtable.xlsx
new file mode 100644
index 0000000..b54c6fb
Binary files /dev/null and b/testdata/bigtable.xlsx differ
diff --git a/testdata/issue47.xls b/testdata/issue47.xls
new file mode 100644
index 0000000..866f246
Binary files /dev/null and b/testdata/issue47.xls differ
diff --git a/testdata/issue47.xlsx b/testdata/issue47.xlsx
new file mode 100644
index 0000000..146e84c
Binary files /dev/null and b/testdata/issue47.xlsx differ