diff --git a/src/support/unicode.cpp b/src/support/unicode.cpp
index 0e773f5327..dec1e9c0c6 100644
--- a/src/support/unicode.cpp
+++ b/src/support/unicode.cpp
@@ -67,7 +67,7 @@ struct IconvProcessor::Impl
 	string tocode_;
 	string fromcode_;
 
-	QMutex mutex_; // iconv() is not thread save
+	QMutex mutex_; // iconv() is not thread save, see #7240
 };