diff --git a/mozilla/mailnews/base/util/nsMsgProtocol.cpp b/mozilla/mailnews/base/util/nsMsgProtocol.cpp
index 3cccd72d522..430b09cc12b 100644
--- a/mozilla/mailnews/base/util/nsMsgProtocol.cpp
+++ b/mozilla/mailnews/base/util/nsMsgProtocol.cpp
@@ -576,8 +576,8 @@ NS_IMETHODIMP nsMsgProtocol::GetContentType(nsACString &aContentType)
 
 NS_IMETHODIMP nsMsgProtocol::SetContentType(const nsACString &aContentType)
 {
-    m_ContentType = aContentType;
-    return NS_OK;
+    nsCAutoString charset;
+    return NS_ParseContentType(aContentType, m_ContentType, charset);
 }
 
 NS_IMETHODIMP nsMsgProtocol::GetContentCharset(nsACString &aContentCharset)
diff --git a/mozilla/mailnews/imap/src/nsImapProtocol.cpp b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
index 476d1f13e47..b6f30e44723 100644
--- a/mozilla/mailnews/imap/src/nsImapProtocol.cpp
+++ b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
@@ -8058,8 +8058,8 @@ NS_IMETHODIMP nsImapMockChannel::GetContentType(nsACString &aContentType)
 
 NS_IMETHODIMP nsImapMockChannel::SetContentType(const nsACString &aContentType)
 {
-  m_ContentType = aContentType;
-  return NS_OK;
+  nsCAutoString charset;
+  return NS_ParseContentType(aContentType, m_ContentType, charset);
 }
 
 NS_IMETHODIMP nsImapMockChannel::GetContentCharset(nsACString &aContentCharset)