--- a/tests/Arbitrary.hs
+++ b/tests/Arbitrary.hs
@@ -46,7 +46,7 @@
 
 -- MPD fields can't contain newlines and the parser skips initial spaces.
 field :: Gen String
-field = (filter (/= '\n') . dropWhile isSpace) <$> arbitrary
+field = (filter (/= '\n') . dropWhile isSpace) . getPrintableString <$> (arbitrary :: Gen PrintableString)
 
 fieldBS :: Gen ByteString
 fieldBS = UTF8.fromString <$> field
