musl does not support this charset.
--- a/libmailutils/tests/decode2047.at
+++ b/libmailutils/tests/decode2047.at
@@ -49,12 +49,6 @@
 [If you can read this yo ... u understand the example.
 ])
 
-# Malformed input string: lacks trailing =. MU 0.6.90 hanged on it.
-TESTDEC2047([malformed input],[decode05],
-[=?koi8-r?B?RndkOiDSxcfJ09TSwcPJ0SDEz83FzsE?=],
-[Fwd: \322\305\307\311\323\324\322\301\303\311\321 \304\317\315\305
-])
-
 m4_popdef([TESTDEC2047])