diff --git a/chart.go b/chart.go
index 5353a32..edfcab7 100644
--- a/chart.go
+++ b/chart.go
@@ -1097,7 +1097,7 @@ func (f *File) drawingParser(drawingXML string, content *xlsxWsDr) int {
 	_, ok := f.XLSX[drawingXML]
 	if ok { // Append Model
 		decodeWsDr := decodeWsDr{}
-		_ = xml.Unmarshal([]byte(f.readXML(drawingXML)), &decodeWsDr)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(drawingXML)), &decodeWsDr)
 		content.R = decodeWsDr.R
 		cNvPrID = len(decodeWsDr.OneCellAnchor) + len(decodeWsDr.TwoCellAnchor) + 1
 		for _, v := range decodeWsDr.OneCellAnchor {
diff --git a/excelize.go b/excelize.go
index d1f0b7f..36a6d8a 100644
--- a/excelize.go
+++ b/excelize.go
@@ -100,7 +100,7 @@ func (f *File) workSheetReader(sheet string) *xlsxWorksheet {
 	}
 	if f.Sheet[name] == nil {
 		var xlsx xlsxWorksheet
-		_ = xml.Unmarshal(f.readXML(name), &xlsx)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(name)), &xlsx)
 		if f.checked == nil {
 			f.checked = make(map[string]bool)
 		}
diff --git a/lib.go b/lib.go
index 865ee29..8e63da9 100644
--- a/lib.go
+++ b/lib.go
@@ -183,3 +183,19 @@ func parseFormatSet(formatSet string) []byte {
 	}
 	return []byte("{}")
 }
+
+// namespaceStrictToTransitional provides a method to convert Strict and
+// Transitional namespaces.
+func namespaceStrictToTransitional(content []byte) []byte {
+	var namespaceTranslationDic = map[string]string{
+		StrictSourceRelationship:         SourceRelationship,
+		StrictSourceRelationshipChart:    SourceRelationshipChart,
+		StrictSourceRelationshipComments: SourceRelationshipComments,
+		StrictSourceRelationshipImage:    SourceRelationshipImage,
+		StrictNameSpaceSpreadSheet:       NameSpaceSpreadSheet,
+	}
+	for s, n := range namespaceTranslationDic {
+		content = bytes.Replace(content, []byte(s), []byte(n), -1)
+	}
+	return content
+}
diff --git a/picture.go b/picture.go
index 8785aaf..9efd875 100644
--- a/picture.go
+++ b/picture.go
@@ -185,7 +185,7 @@ func (f *File) addSheetRelationships(sheet, relType, target, targetMode string)
 	_, ok = f.XLSX[rels]
 	if ok {
 		ID.Reset()
-		_ = xml.Unmarshal([]byte(f.readXML(rels)), &sheetRels)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(rels)), &sheetRels)
 		rID = len(sheetRels.Relationships) + 1
 		ID.WriteString("rId")
 		ID.WriteString(strconv.Itoa(rID))
@@ -211,7 +211,7 @@ func (f *File) deleteSheetRelationships(sheet, rID string) {
 	}
 	var rels = "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
 	var sheetRels xlsxWorkbookRels
-	_ = xml.Unmarshal([]byte(f.readXML(rels)), &sheetRels)
+	_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(rels)), &sheetRels)
 	for k, v := range sheetRels.Relationships {
 		if v.ID == rID {
 			sheetRels.Relationships = append(sheetRels.Relationships[:k], sheetRels.Relationships[k+1:]...)
@@ -328,7 +328,7 @@ func (f *File) addDrawingRelationships(index int, relType, target, targetMode st
 	_, ok := f.XLSX[rels]
 	if ok {
 		ID.Reset()
-		_ = xml.Unmarshal([]byte(f.readXML(rels)), &drawingRels)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(rels)), &drawingRels)
 		rID = len(drawingRels.Relationships) + 1
 		ID.WriteString("rId")
 		ID.WriteString(strconv.Itoa(rID))
@@ -448,7 +448,7 @@ func (f *File) getSheetRelationshipsTargetByID(sheet, rID string) string {
 	}
 	var rels = "xl/worksheets/_rels/" + strings.TrimPrefix(name, "xl/worksheets/") + ".rels"
 	var sheetRels xlsxWorkbookRels
-	_ = xml.Unmarshal([]byte(f.readXML(rels)), &sheetRels)
+	_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(rels)), &sheetRels)
 	for _, v := range sheetRels.Relationships {
 		if v.ID == rID {
 			return v.Target
@@ -488,7 +488,7 @@ func (f *File) GetPicture(sheet, cell string) (string, []byte) {
 		return "", nil
 	}
 	decodeWsDr := decodeWsDr{}
-	_ = xml.Unmarshal([]byte(f.readXML(drawingXML)), &decodeWsDr)
+	_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(drawingXML)), &decodeWsDr)
 
 	cell = strings.ToUpper(cell)
 	fromCol := string(strings.Map(letterOnlyMapF, cell))
@@ -523,7 +523,7 @@ func (f *File) getDrawingRelationships(rels, rID string) *xlsxWorkbookRelation {
 		return nil
 	}
 	var drawingRels xlsxWorkbookRels
-	_ = xml.Unmarshal([]byte(f.readXML(rels)), &drawingRels)
+	_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(rels)), &drawingRels)
 	for _, v := range drawingRels.Relationships {
 		if v.ID == rID {
 			return &v
diff --git a/sheet.go b/sheet.go
index 2344218..7b97d3e 100644
--- a/sheet.go
+++ b/sheet.go
@@ -51,7 +51,7 @@ func (f *File) NewSheet(name string) int {
 func (f *File) contentTypesReader() *xlsxTypes {
 	if f.ContentTypes == nil {
 		var content xlsxTypes
-		_ = xml.Unmarshal([]byte(f.readXML("[Content_Types].xml")), &content)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("[Content_Types].xml")), &content)
 		f.ContentTypes = &content
 	}
 	return f.ContentTypes
@@ -71,7 +71,7 @@ func (f *File) contentTypesWriter() {
 func (f *File) workbookReader() *xlsxWorkbook {
 	if f.WorkBook == nil {
 		var content xlsxWorkbook
-		_ = xml.Unmarshal([]byte(f.readXML("xl/workbook.xml")), &content)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("xl/workbook.xml")), &content)
 		f.WorkBook = &content
 	}
 	return f.WorkBook
@@ -162,7 +162,7 @@ func (f *File) setWorkbook(name string, rid int) {
 func (f *File) workbookRelsReader() *xlsxWorkbookRels {
 	if f.WorkBookRels == nil {
 		var content xlsxWorkbookRels
-		_ = xml.Unmarshal([]byte(f.readXML("xl/_rels/workbook.xml.rels")), &content)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("xl/_rels/workbook.xml.rels")), &content)
 		f.WorkBookRels = &content
 	}
 	return f.WorkBookRels
@@ -267,7 +267,7 @@ func (f *File) GetActiveSheetIndex() int {
 		buffer.WriteString("xl/worksheets/sheet")
 		buffer.WriteString(strings.TrimPrefix(v.ID, "rId"))
 		buffer.WriteString(".xml")
-		_ = xml.Unmarshal([]byte(f.readXML(buffer.String())), &xlsx)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(buffer.String())), &xlsx)
 		for _, sheetView := range xlsx.SheetViews.SheetView {
 			if sheetView.TabSelected {
 				ID, _ := strconv.Atoi(strings.TrimPrefix(v.ID, "rId"))
diff --git a/styles.go b/styles.go
index 513fc9b..f923787 100644
--- a/styles.go
+++ b/styles.go
@@ -999,7 +999,7 @@ func is12HourTime(format string) bool {
 func (f *File) stylesReader() *xlsxStyleSheet {
 	if f.Styles == nil {
 		var styleSheet xlsxStyleSheet
-		_ = xml.Unmarshal([]byte(f.readXML("xl/styles.xml")), &styleSheet)
+		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("xl/styles.xml")), &styleSheet)
 		f.Styles = &styleSheet
 	}
 	return f.Styles
@@ -2757,7 +2757,7 @@ func getPaletteColor(color string) string {
 // structure after deserialization.
 func (f *File) themeReader() *xlsxTheme {
 	var theme xlsxTheme
-	_ = xml.Unmarshal([]byte(f.readXML("xl/theme/theme1.xml")), &theme)
+	_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("xl/theme/theme1.xml")), &theme)
 	return &theme
 }
 
diff --git a/test/Book1.xlsx b/test/Book1.xlsx
index 84c43d1..7d9886e 100755
Binary files a/test/Book1.xlsx and b/test/Book1.xlsx differ
diff --git a/xmlDrawing.go b/xmlDrawing.go
index 6ba7d31..7356cb5 100644
--- a/xmlDrawing.go
+++ b/xmlDrawing.go
@@ -13,24 +13,29 @@ import "encoding/xml"
 
 // Source relationship and namespace.
 const (
-	SourceRelationship              = "http://schemas.openxmlformats.org/officeDocument/2006/relationships"
-	SourceRelationshipChart         = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/chart"
-	SourceRelationshipComments      = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/comments"
-	SourceRelationshipImage         = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
-	SourceRelationshipTable         = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/table"
-	SourceRelationshipDrawingML     = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/drawing"
-	SourceRelationshipDrawingVML    = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/vmlDrawing"
-	SourceRelationshipHyperLink     = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink"
-	SourceRelationshipWorkSheet     = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet"
-	SourceRelationshipChart201506   = "http://schemas.microsoft.com/office/drawing/2015/06/chart"
-	SourceRelationshipChart20070802 = "http://schemas.microsoft.com/office/drawing/2007/8/2/chart"
-	SourceRelationshipChart2014     = "http://schemas.microsoft.com/office/drawing/2014/chart"
-	SourceRelationshipCompatibility = "http://schemas.openxmlformats.org/markup-compatibility/2006"
-	NameSpaceDrawingML              = "http://schemas.openxmlformats.org/drawingml/2006/main"
-	NameSpaceDrawingMLChart         = "http://schemas.openxmlformats.org/drawingml/2006/chart"
-	NameSpaceDrawingMLSpreadSheet   = "http://schemas.openxmlformats.org/drawingml/2006/spreadsheetDrawing"
-	NameSpaceSpreadSheet            = "http://schemas.openxmlformats.org/spreadsheetml/2006/main"
-	NameSpaceXML                    = "http://www.w3.org/XML/1998/namespace"
+	SourceRelationship               = "http://schemas.openxmlformats.org/officeDocument/2006/relationships"
+	SourceRelationshipChart          = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/chart"
+	SourceRelationshipComments       = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/comments"
+	SourceRelationshipImage          = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/image"
+	SourceRelationshipTable          = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/table"
+	SourceRelationshipDrawingML      = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/drawing"
+	SourceRelationshipDrawingVML     = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/vmlDrawing"
+	SourceRelationshipHyperLink      = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/hyperlink"
+	SourceRelationshipWorkSheet      = "http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet"
+	SourceRelationshipChart201506    = "http://schemas.microsoft.com/office/drawing/2015/06/chart"
+	SourceRelationshipChart20070802  = "http://schemas.microsoft.com/office/drawing/2007/8/2/chart"
+	SourceRelationshipChart2014      = "http://schemas.microsoft.com/office/drawing/2014/chart"
+	SourceRelationshipCompatibility  = "http://schemas.openxmlformats.org/markup-compatibility/2006"
+	NameSpaceDrawingML               = "http://schemas.openxmlformats.org/drawingml/2006/main"
+	NameSpaceDrawingMLChart          = "http://schemas.openxmlformats.org/drawingml/2006/chart"
+	NameSpaceDrawingMLSpreadSheet    = "http://schemas.openxmlformats.org/drawingml/2006/spreadsheetDrawing"
+	NameSpaceSpreadSheet             = "http://schemas.openxmlformats.org/spreadsheetml/2006/main"
+	NameSpaceXML                     = "http://www.w3.org/XML/1998/namespace"
+	StrictSourceRelationship         = "http://purl.oclc.org/ooxml/officeDocument/relationships"
+	StrictSourceRelationshipChart    = "http://purl.oclc.org/ooxml/officeDocument/relationships/chart"
+	StrictSourceRelationshipComments = "http://purl.oclc.org/ooxml/officeDocument/relationships/comments"
+	StrictSourceRelationshipImage    = "http://purl.oclc.org/ooxml/officeDocument/relationships/image"
+	StrictNameSpaceSpreadSheet       = "http://purl.oclc.org/ooxml/spreadsheetml/main"
 )
 
 var supportImageTypes = map[string]string{".gif": ".gif", ".jpg": ".jpeg", ".jpeg": ".jpeg", ".png": ".png"}