Take from: https://github.com/dbmail/dbmail/commit/01d5d422f88c5edd6f1f77787cd6459d756d00b4

--- a/src/dm_mailboxstate.c
+++ b/src/dm_mailboxstate.c
@@ -643,7 +643,7 @@
 
 gboolean MailboxState_hasKeyword(T M, const char *keyword)
 {
-	if (g_list_find_custom(M->keywords, (gpointer)keyword, dm_strcmpdata))
+	if (g_list_find_custom(M->keywords, (gpointer)keyword, (GCompareFunc) dm_strcmpdata))
 		return TRUE;
 	return FALSE;
 }