diff --git a/mozilla/content/base/src/nsScriptLoader.cpp b/mozilla/content/base/src/nsScriptLoader.cpp
index 0808104d890..cd621de819b 100644
--- a/mozilla/content/base/src/nsScriptLoader.cpp
+++ b/mozilla/content/base/src/nsScriptLoader.cpp
@@ -691,6 +691,11 @@ nsScriptLoader::OnStreamComplete(nsIStreamLoader* aLoader,
 
     NS_ASSERTION(NS_SUCCEEDED(rv), "Could not get document charset!");
 
+    if (characterSet.IsEmpty()) {
+      // fall back to ISO-8851-1, see bug 118404
+      characterSet = NS_LITERAL_STRING("ISO-8859-1");
+    }
+    
     nsCOMPtr<nsICharsetConverterManager> charsetConv =
       do_GetService(kCharsetConverterManagerCID, &rv);
 
diff --git a/mozilla/content/html/document/src/nsHTMLDocument.cpp b/mozilla/content/html/document/src/nsHTMLDocument.cpp
index 38fc1d01706..4135b1f2feb 100644
--- a/mozilla/content/html/document/src/nsHTMLDocument.cpp
+++ b/mozilla/content/html/document/src/nsHTMLDocument.cpp
@@ -679,11 +679,11 @@ nsHTMLDocument::TryWeakDocTypeDefault(PRInt32& aCharsetSource,
   if (prefs) {
     nsXPIDLString defCharset;
     nsresult rv = prefs->GetLocalizedUnicharPref("intl.charset.default", getter_Copies(defCharset));
-    if (NS_SUCCEEDED(rv)) {
+    if (NS_SUCCEEDED(rv) && !defCharset.IsEmpty()) {
       aCharset.Assign(defCharset);
+      aCharsetSource = kCharsetFromWeakDocTypeDefault;
     }
   }
-  aCharsetSource = kCharsetFromWeakDocTypeDefault;
   return PR_TRUE;
 }