diff --git a/lib/mu-msg-iter.cc b/lib/mu-msg-iter.cc
index 0d5e7d49..b7099d13 100644
--- a/lib/mu-msg-iter.cc
+++ b/lib/mu-msg-iter.cc
@@ -359,14 +359,16 @@ mu_msg_iter_get_docid (MuMsgIter *iter)
 
 
 
-const char*
+char*
 mu_msg_iter_get_msgid (MuMsgIter *iter)
 {
 	g_return_val_if_fail (iter, NULL);
 	g_return_val_if_fail (!mu_msg_iter_is_done(iter), NULL);
 
 	try {
-		return iter->msgid().c_str();
+		const char *msgid (iter->msgid().c_str());
+
+		return msgid ? g_strdup (msgid) : NULL;
 
 	} MU_XAPIAN_CATCH_BLOCK_RETURN (NULL);
 }
@@ -388,7 +390,7 @@ mu_msg_iter_get_refs (MuMsgIter *iter)
 	} MU_XAPIAN_CATCH_BLOCK_RETURN (NULL);
 }
 
-const char*
+char*
 mu_msg_iter_get_thread_id (MuMsgIter *iter)
 {
 	g_return_val_if_fail (iter, NULL);
@@ -397,7 +399,8 @@ mu_msg_iter_get_thread_id (MuMsgIter *iter)
 	try {
 		const std::string thread_id (
 			iter->cursor().get_document().get_value(MU_MSG_FIELD_ID_THREAD_ID).c_str());
-		return thread_id.empty() ? NULL : thread_id.c_str();
+		
+		return thread_id.empty() ? NULL : g_strdup (thread_id.c_str());
 
 
 	} MU_XAPIAN_CATCH_BLOCK_RETURN (NULL);
diff --git a/lib/mu-msg-iter.h b/lib/mu-msg-iter.h
index f98d8d81..49d35d95 100644
--- a/lib/mu-msg-iter.h
+++ b/lib/mu-msg-iter.h
@@ -145,7 +145,7 @@ void mu_msg_iter_set_preferred (MuMsgIter *iter, GHashTable *preferred_hash);
  *
  * @return the docid or (unsigned int)-1 in case of error
  */
-unsigned int     mu_msg_iter_get_docid         (MuMsgIter *iter);
+guint    mu_msg_iter_get_docid         (MuMsgIter *iter);
 
 
 /**
@@ -196,10 +196,10 @@ const MuMsgIterThreadInfo* mu_msg_iter_get_thread_info (MuMsgIter *iter);
  *
  * @param iter a valid MuMsgIter iterator
  *
- * @return the message-id; this only stays valid as long as the
- * current iter stays valid.
+ * @return the message-id; free with g_free().
  */
-const char* mu_msg_iter_get_msgid (MuMsgIter *iter);
+char* mu_msg_iter_get_msgid (MuMsgIter *iter)
+	G_GNUC_WARN_UNUSED_RESULT;
 
 /**
  * get the list of references for this messages as a NULL-terminated
@@ -210,7 +210,8 @@ const char* mu_msg_iter_get_msgid (MuMsgIter *iter);
  * @return a NULL-terminated string array. free with g_strfreev when
  * it's no longer needed.
  */
-char** mu_msg_iter_get_refs (MuMsgIter *iter);
+char** mu_msg_iter_get_refs (MuMsgIter *iter)
+	G_GNUC_WARN_UNUSED_RESULT;
 
 
 /**
@@ -218,15 +219,10 @@ char** mu_msg_iter_get_refs (MuMsgIter *iter);
  *
  * @param iter a valid MuMsgIter iterator
  *
- * @return the thread-id; this only stays valid as long as the
- * current iter stays valid.
+ * @return the thread-id; free with g_free().
  */
-const char* mu_msg_iter_get_thread_id (MuMsgIter *iter);
-
-
-
-
-
+char* mu_msg_iter_get_thread_id (MuMsgIter *iter)
+	G_GNUC_WARN_UNUSED_RESULT;
 
 
 /* FIXME */
diff --git a/lib/mu-query.cc b/lib/mu-query.cc
index f6c4bec7..5761f2a0 100644
--- a/lib/mu-query.cc
+++ b/lib/mu-query.cc
@@ -414,22 +414,23 @@ static GHashTable*
 get_thread_ids (MuMsgIter *iter, GHashTable **orig_set)
 {
 	GHashTable *ids;
+	
 	ids	  = g_hash_table_new_full (g_str_hash, g_str_equal,
 					   (GDestroyNotify)g_free, NULL);
 	*orig_set = g_hash_table_new_full (g_str_hash, g_str_equal,
 					   (GDestroyNotify)g_free, NULL);
 
 	while (!mu_msg_iter_is_done (iter)) {
-		const char *thread_id, *msgid;
-		unsigned docid;
+		char		*thread_id, *msgid;
+		unsigned	 docid;
 		/* record the thread id for the message */
 		if ((thread_id = mu_msg_iter_get_thread_id (iter)))
-			g_hash_table_insert (ids, g_strdup (thread_id),
+			g_hash_table_insert (ids, thread_id,
 					     GSIZE_TO_POINTER(TRUE));
 		/* record the original set */
 		docid = mu_msg_iter_get_docid(iter);
 		if (docid != 0 && (msgid = mu_msg_iter_get_msgid (iter)))
-			g_hash_table_insert (*orig_set, g_strdup (msgid),
+			g_hash_table_insert (*orig_set, msgid,
 					     GSIZE_TO_POINTER(docid));
 
 		if (!mu_msg_iter_next (iter))