--- a/mailnews/base/util/nsMsgProtocol.cpp
+++ b/mailnews/base/util/nsMsgProtocol.cpp
@@ -682,17 +682,17 @@ nsMsgProtocol::GetContentDisposition(PRU
 
 NS_IMETHODIMP
 nsMsgProtocol::GetContentDispositionFilename(nsAString &aContentDispositionFilename)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsMsgProtocol::GetContentDispositionHeader(nsAString &aContentDispositionHeader)
+nsMsgProtocol::GetContentDispositionHeader(nsACString &aContentDispositionHeader)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP nsMsgProtocol::GetContentLength(PRInt32 *aContentLength)
 {
   *aContentLength = mContentLength;
   return NS_OK;

--- a/mailnews/imap/src/nsImapProtocol.cpp
+++ b/mailnews/imap/src/nsImapProtocol.cpp
@@ -9410,17 +9410,17 @@ nsImapMockChannel::GetContentDisposition
 
 NS_IMETHODIMP
 nsImapMockChannel::GetContentDispositionFilename(nsAString &aContentDispositionFilename)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsImapMockChannel::GetContentDispositionHeader(nsAString &aContentDispositionHeader)
+nsImapMockChannel::GetContentDispositionHeader(nsACString &aContentDispositionHeader)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP nsImapMockChannel::GetContentLength(PRInt32 * aContentLength)
 {
   *aContentLength = mContentLength;
   return NS_OK;

--- a/mailnews/news/src/nsNntpMockChannel.cpp
+++ b/mailnews/news/src/nsNntpMockChannel.cpp
@@ -243,17 +243,17 @@ nsNntpMockChannel::GetContentDisposition
 
 NS_IMETHODIMP
 nsNntpMockChannel::GetContentDispositionFilename(nsAString &aContentDispositionFilename)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP
-nsNntpMockChannel::GetContentDispositionHeader(nsAString &aContentDispositionHeader)
+nsNntpMockChannel::GetContentDispositionHeader(nsACString &aContentDispositionHeader)
 {
   return NS_ERROR_NOT_AVAILABLE;
 }
 
 NS_IMETHODIMP nsNntpMockChannel::GetContentLength(PRInt32 *length)
 {
   FORWARD_CALL(GetContentLength, length)
   *length = m_contentLength;