diff --git a/src/util/error.cpp b/src/util/error.cpp
index 7d614dca..c09dc703 100644
--- a/src/util/error.cpp
+++ b/src/util/error.cpp
@@ -29,6 +29,7 @@ DECLARE_TYPEOF_COLLECTION(String);
 
 void handle_error(const String& e, bool allow_duplicate = true, bool now = true) {
 	// Check duplicates
+	// TODO: thread safety
 	if (!allow_duplicate) {
 		FOR_EACH(pe, previous_errors) {
 			if (e == pe)  return;