diff --git a/dom/mobilemessage/interfaces/nsIDOMMozMmsMessage.idl b/dom/mobilemessage/interfaces/nsIDOMMozMmsMessage.idl
index 5d7ed281a10d..0b921be210c3 100644
--- a/dom/mobilemessage/interfaces/nsIDOMMozMmsMessage.idl
+++ b/dom/mobilemessage/interfaces/nsIDOMMozMmsMessage.idl
@@ -11,8 +11,7 @@ dictionary MmsAttachment
 {
   DOMString? id;
   DOMString? location;
-  nsIDOMBlob content; // If the content blob is a text/plain type, the encoding
-                      // for text should always be "utf-8".
+  nsIDOMBlob content;
 };
 
 [scriptable, builtinclass, uuid(2e5e1c16-b7af-11e2-af04-8f4b1610a600)]
diff --git a/dom/mobilemessage/src/ril/WspPduHelper.jsm b/dom/mobilemessage/src/ril/WspPduHelper.jsm
index 0613b50d0907..7047d905eec5 100644
--- a/dom/mobilemessage/src/ril/WspPduHelper.jsm
+++ b/dom/mobilemessage/src/ril/WspPduHelper.jsm
@@ -2292,40 +2292,18 @@ this.PduHelper = {
         let octetArray = Octet.decodeMultiple(data, contentEnd);
         let content = null;
         if (octetArray) {
-          let charset = headers["content-type"].params &&
-                        headers["content-type"].params.charset
-                      ? headers["content-type"].params.charset.charset
-                      : null;
-
-          let mimeType = headers["content-type"].media;
-
-          if (mimeType) {
-            if (mimeType == "application/smil") {
-              // If the content is a SMIL type, convert it to a string.
-              // We hope to save and expose the SMIL content in a string way.
-              content = this.decodeStringContent(octetArray, charset);
-            } else if (mimeType.indexOf("text/") == 0 && charset != "utf-8") {
-              // If the content is a "text/plain" type, we have to make sure
-              // the encoding of the blob content should always be "utf-8".
-              let tmpStr = this.decodeStringContent(octetArray, charset);
-              let encoder = new TextEncoder("UTF-8");
-              content = new Blob([encoder.encode(tmpStr)], {type : mimeType});
-
-              // Make up the missing encoding info.
-              if (!headers["content-type"].params) {
-                headers["content-type"].params = {};
-              }
-              if (!headers["content-type"].params.charset) {
-                headers["content-type"].params.charset = {};
-              }
-              if (!headers["content-type"].params.charset.charset) {
-                headers["content-type"].params.charset.charset = "utf-8";
-              }
-            }
+          // If the content is a SMIL type, convert it to a string.
+          // We hope to save and expose the SMIL content as a string way.
+          if (headers["content-type"].media == "application/smil") {
+            let charset = headers["content-type"].params &&
+                          headers["content-type"].params.charset
+                        ? headers["content-type"].params.charset["charset"]
+                        : null;
+            content = this.decodeStringContent(octetArray, charset);
           }
-
           if (!content) {
-            content = new Blob([octetArray], {type : mimeType});
+            content = new Blob([octetArray],
+                               {type : headers["content-type"].media});
           }
         }