diff --git a/client/deps/tinycbor/cbor.h b/client/deps/tinycbor/cbor.h
index 081597fec..6890ee597 100644
--- a/client/deps/tinycbor/cbor.h
+++ b/client/deps/tinycbor/cbor.h
@@ -555,6 +555,7 @@ enum CborPrettyFlags {
     CborPrettyDefaultFlags          = CborPrettyIndicateIndeterminateLength
 };
 
+/* cf  https://sourceforge.net/p/mingw-w64/wiki2/gnu%20printf/ */
 typedef CborError(*CborStreamFunction)(void *token, const char *fmt, ...)
 #if defined(__MINGW32__) || defined(__MINGW64__)
     __attribute__((format (__MINGW_PRINTF_FORMAT, 2, 3)));