diff --git a/src/documentation/content/xdocs/status.xml b/src/documentation/content/xdocs/status.xml
index 0d13e0b3c..90fdb8838 100644
--- a/src/documentation/content/xdocs/status.xml
+++ b/src/documentation/content/xdocs/status.xml
@@ -34,6 +34,7 @@
 
     <changes>
         <release version="3.9-beta1" date="2012-??-??">
+          <action dev="poi-developers" type="fix">52211 - avoid unnessary re-coverting content types to US-ASCII, it can cause exceptions on ibm mainframes</action>
           <action dev="poi-developers" type="fix">53568 - Set shapes anchors in XSSF when reading from existing drawings</action>
           <action dev="poi-developers" type="add">HSSFOptimiser will now also tidy away un-used cell styles, in addition to duplicate styles</action>
           <action dev="poi-developers" type="fix">53493 - Fixed memory and temporary file leak in SXSSF </action>
diff --git a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentType.java b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentType.java
index ecf45af54..4d4c9283c 100644
--- a/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentType.java
+++ b/src/ooxml/java/org/apache/poi/openxml4j/opc/internal/ContentType.java
@@ -134,16 +134,7 @@ public final class ContentType {
 	 *             If the specified content type is not valid with RFC 2616.
 	 */
 	public ContentType(String contentType) throws InvalidFormatException {
-		// Conversion en US-ASCII
-		String contentTypeASCII = null;
-		try {
-			contentTypeASCII = new String(contentType.getBytes(), "US-ASCII");
-		} catch (UnsupportedEncodingException e) {
-			throw new InvalidFormatException(
-					"The specified content type is not an ASCII value.");
-		}
-
-		Matcher mMediaType = patternMediaType.matcher(contentTypeASCII);
+		Matcher mMediaType = patternMediaType.matcher(contentType);
 		if (!mMediaType.matches())
 			throw new InvalidFormatException(
 					"The specified content type '"
diff --git a/src/ooxml/testcases/org/apache/poi/openxml4j/opc/TestContentType.java b/src/ooxml/testcases/org/apache/poi/openxml4j/opc/TestContentType.java
index 257f4015d..ab2d6aa71 100644
--- a/src/ooxml/testcases/org/apache/poi/openxml4j/opc/TestContentType.java
+++ b/src/ooxml/testcases/org/apache/poi/openxml4j/opc/TestContentType.java
@@ -85,7 +85,9 @@ public final class TestContentType extends TestCase {
 	 */
 	public void testContentTypeParameterFailure() {
 		String[] contentTypesToTest = new String[] { "mail/toto;titi=tata",
-				"text/xml;a=b;c=d", "mail/toto;\"titi=tata\"" };
+				"text/xml;a=b;c=d", "mail/toto;\"titi=tata\"",
+                "text/\u0080" // characters above ASCII are not allowed
+        };
 		for (int i = 0; i < contentTypesToTest.length; ++i) {
 			try {
 				new ContentType(contentTypesToTest[i]);