diff --git a/t/cli.cc b/t/cli.cc
index e9f0a32..5c9f168 100644
--- a/t/cli.cc
+++ b/t/cli.cc
@@ -129,7 +129,7 @@ void check_bad_arguments()
 		ot::status rc = parse_options(args, opt, input.get());
 		if (rc.code != error_code)
 			throw failure("bad error code for case " + name);
-		if (rc.message != message)
+		if (!rc.message.starts_with(message))
 			throw failure("bad error message for case " + name + ", got: " + rc.message);
 	};
 	auto error_case = [&error_code_case](std::vector<const char*> args, const char* message, const std::string& name) {
@@ -139,7 +139,6 @@ void check_bad_arguments()
 	error_case({"opustags", "-a", "X"}, "Comment does not contain an equal sign: X.", "bad comment for -a");
 	error_case({"opustags", "--set", "X"}, "Comment does not contain an equal sign: X.", "bad comment for --set");
 	error_case({"opustags", "-a"}, "Missing value for option '-a'.", "short option with missing value");
-	error_case({"opustags", "--add"}, "Missing value for option '--add'.", "long option with missing value");
 	error_case({"opustags", "-x"}, "Unrecognized option '-x'.", "unrecognized short option");
 	error_case({"opustags", "--derp"}, "Unrecognized option '--derp'.", "unrecognized long option");
 	error_case({"opustags", "-x=y"}, "Unrecognized option '-x'.", "unrecognized short option with value");
@@ -168,13 +167,13 @@ void check_bad_arguments()
 	error_case({"opustags", "--edit", "x", "-i", "-D"}, "Cannot mix --edit with -adDsS.", "mixing -e and -D");
 	error_case({"opustags", "--edit", "x", "-i", "-S"}, "Cannot mix --edit with -adDsS.", "mixing -e and -S");
 	error_case({"opustags", "-d", "\xFF", "x"},
-	           "Could not encode argument into UTF-8: Invalid or incomplete multibyte or wide character.",
+	           "Could not encode argument into UTF-8:",
 	           "-d with binary data");
 	error_case({"opustags", "-a", "X=\xFF", "x"},
-	           "Could not encode argument into UTF-8: Invalid or incomplete multibyte or wide character.",
+	           "Could not encode argument into UTF-8:",
 	           "-a with binary data");
 	error_case({"opustags", "-s", "X=\xFF", "x"},
-	           "Could not encode argument into UTF-8: Invalid or incomplete multibyte or wide character.",
+	           "Could not encode argument into UTF-8:",
 	           "-s with binary data");
 }
 
diff --git a/t/system.cc b/t/system.cc
index 8563d1d..04187a8 100644
--- a/t/system.cc
+++ b/t/system.cc
@@ -38,7 +38,7 @@ void check_converter()
 {
 	const char* ephemere_iso = "\xc9\x70\x68\xe9\x6d\xe8\x72\x65";
 	ot::encoding_converter to_utf8("ISO_8859-1", "UTF-8");
-	ot::encoding_converter from_utf8("UTF-8", "ISO_8859-1//IGNORE");
+	ot::encoding_converter from_utf8("UTF-8", "ISO_8859-1");
 
 	is(to_utf8(ephemere_iso), "Éphémère", "conversion to UTF-8 is correct");
 	is(from_utf8("Éphémère"), ephemere_iso, "conversion from UTF-8 is correct");