diff --git a/mailnews/extensions/bayesian-spam-filter/src/nsBayesianFilter.cpp b/mailnews/extensions/bayesian-spam-filter/src/nsBayesianFilter.cpp
index d0336db1dc..f879c7aa34 100644
--- a/mailnews/extensions/bayesian-spam-filter/src/nsBayesianFilter.cpp
+++ b/mailnews/extensions/bayesian-spam-filter/src/nsBayesianFilter.cpp
@@ -510,13 +510,13 @@ void Tokenizer::tokenizeHeaders(nsIUTF8StringEnumerator * aHeaderNames, nsIUTF8S
 
           // extract the charset parameter
           nsCString parameterValue;
-          mimehdrpar->GetParameterInternal(headerValue.get(), "charset", nullptr, nullptr, getter_Copies(parameterValue));
+          mimehdrpar->GetParameterInternal(headerValue, "charset", nullptr, nullptr, getter_Copies(parameterValue));
           addTokenForHeader("charset", parameterValue);
 
           // create a token containing just the content type
-          mimehdrpar->GetParameterInternal(headerValue.get(), "type", nullptr, nullptr, getter_Copies(parameterValue));
+          mimehdrpar->GetParameterInternal(headerValue, "type", nullptr, nullptr, getter_Copies(parameterValue));
           if (!parameterValue.Length())
-            mimehdrpar->GetParameterInternal(headerValue.get(), nullptr /* use first unnamed param */, nullptr, nullptr, getter_Copies(parameterValue));
+            mimehdrpar->GetParameterInternal(headerValue, nullptr /* use first unnamed param */, nullptr, nullptr, getter_Copies(parameterValue));
           addTokenForHeader("content-type/type", parameterValue);
 
           // XXX: should we add a token for the entire content-type header as well or just these parts we have extracted?
diff --git a/mailnews/mime/src/mimehdrs.cpp b/mailnews/mime/src/mimehdrs.cpp
index 6d187ed529..92452bfb00 100644
--- a/mailnews/mime/src/mimehdrs.cpp
+++ b/mailnews/mime/src/mimehdrs.cpp
@@ -493,8 +493,9 @@ MimeHeaders_get_parameter (const char *header_value, const char *parm_name,
   if (NS_FAILED(rv))
     return nullptr;
 
+  nsCString hdr_value(header_value);
   nsCString result;
-  rv = mimehdrpar->GetParameterInternal(header_value, parm_name, charset,
+  rv = mimehdrpar->GetParameterInternal(hdr_value, parm_name, charset,
                                         language, getter_Copies(result));
   return NS_SUCCEEDED(rv) ? PL_strdup(result.get()) : nullptr;
 }