--- a/src/internfile/mimehandler.cpp
+++ b/src/internfile/mimehandler.cpp
@@ -42,6 +42,11 @@
// handlers. There can be several instances for a given mime type
// (think email attachment in email message: 2 rfc822 handlers are
// needed simulteanously)
+//
+// FIXME: this is not compatible with multiple threads and a potential
+// problem in the recoll gui (indexing thread + preview request). A
+// simple lock would be enough as handlers are removed from the cache
+// while in use and multiple copies are allowed
static multimap<string, Dijon::Filter*> o_handlers;
/** For mime types set as "internal" in mimeconf: