diff --git a/netwerk/mime/nsMIMEHeaderParamImpl.cpp b/netwerk/mime/nsMIMEHeaderParamImpl.cpp
index 3c3ec117b0b0..4bc5414a6486 100644
--- a/netwerk/mime/nsMIMEHeaderParamImpl.cpp
+++ b/netwerk/mime/nsMIMEHeaderParamImpl.cpp
@@ -144,22 +144,25 @@ void RemoveQuotedStringEscapes(char *src)
 class Continuation {
   public:
     Continuation(const char *aValue, PRUint32 aLength,
-                 bool aNeedsPercentDecoding) {
+                 bool aNeedsPercentDecoding, bool aWasQuotedString) {
       value = aValue;
       length = aLength;
       needsPercentDecoding = aNeedsPercentDecoding;
+      wasQuotedString = aWasQuotedString;
     }
     Continuation() {
       // empty constructor needed for nsTArray
       value = 0L;
       length = 0;
       needsPercentDecoding = false;
+      wasQuotedString = false;
     }
     ~Continuation() {}
 
     const char *value;
     PRUint32 length;
     bool needsPercentDecoding;
+    bool wasQuotedString;
 };
 
 // combine segments into a single string, returning the allocated string
@@ -192,6 +195,9 @@ char *combineContinuations(nsTArray<Continuation>& aArray)
       if (cont.needsPercentDecoding) {
         nsUnescape(c);
       }
+      if (cont.wasQuotedString) {
+        RemoveQuotedStringEscapes(c);
+      }
     }
 
     // return null if empty value
@@ -210,7 +216,7 @@ char *combineContinuations(nsTArray<Continuation>& aArray)
 // add a continuation, return false on error if segment already has been seen
 bool addContinuation(nsTArray<Continuation>& aArray, PRUint32 aIndex,
                      const char *aValue, PRUint32 aLength,
-                     bool aNeedsPercentDecoding)
+                     bool aNeedsPercentDecoding, bool aWasQuotedString)
 {
   if (aIndex < aArray.Length() && aArray[aIndex].value) {
     NS_WARNING("duplicate RC2231 continuation segment #\n");
@@ -222,7 +228,12 @@ bool addContinuation(nsTArray<Continuation>& aArray, PRUint32 aIndex,
     return false;
   }
 
-  Continuation cont (aValue, aLength, aNeedsPercentDecoding);
+  if (aNeedsPercentDecoding && aWasQuotedString) {
+    NS_WARNING("RC2231 continuation segment can't use percent encoding and quoted string form at the same time\n");
+    return false;
+  }
+
+  Continuation cont(aValue, aLength, aNeedsPercentDecoding, aWasQuotedString);
 
   if (aArray.Length() <= aIndex) {
     aArray.SetLength(aIndex + 1);
@@ -578,7 +589,8 @@ nsMIMEHeaderParamImpl::DoParameterInternal(const char *aHeaderValue,
           } else {
             // caseC
             bool added = addContinuation(segments, 0, rawValStart,
-                                         rawValLength, needExtDecoding);
+                                         rawValLength, needExtDecoding,
+                                         isQuotedString);
 
             if (!added) {
               // continuation not added, stop processing them
@@ -593,7 +605,8 @@ nsMIMEHeaderParamImpl::DoParameterInternal(const char *aHeaderValue,
         PRUint32 valueLength = valueEnd - valueStart;
 
         bool added = addContinuation(segments, segmentNumber, valueStart,
-                                     valueLength, needExtDecoding);
+                                     valueLength, needExtDecoding,
+                                     isQuotedString);
 
         if (!added) {
           // continuation not added, stop processing them
diff --git a/netwerk/test/unit/test_MIME_params.js b/netwerk/test/unit/test_MIME_params.js
index 0e53dbc80788..8fee955b6b63 100644
--- a/netwerk/test/unit/test_MIME_params.js
+++ b/netwerk/test/unit/test_MIME_params.js
@@ -385,6 +385,17 @@ var tests = [
   ["attachment", 
    "attachment", Cr.NS_ERROR_INVALID_ARG], 
 
+  // Bug 730574: quoted-string in RFC2231-continuations not handled
+
+  ['attachment; filename=basic; filename*0="foo"; filename*1="\\b\\a\\r.html"', 
+   "attachment", "foobar.html",
+   "attachment", "basic"],
+
+  // unmatched escape char
+  ['attachment; filename=basic; filename*0="foo"; filename*1="\\b\\a\\', 
+   "attachment", "fooba\\",
+   "attachment", "basic"],
+
   // Bug 732369: Content-Disposition parser does not require presence of ";" between params
 
   ["attachment; extension=bla filename=foo",