diff --git a/t/op/string.t b/t/op/string.t
index d59572eeed..65e65bcfc0 100644
--- a/t/op/string.t
+++ b/t/op/string.t
@@ -1611,6 +1611,19 @@ catch2:
     pop_eh
 null2:
     is ($S9, "Can't upcase NULL string", 'upcase inplace null')
+
+    push_eh catch3
+    null $S9
+    set $S0, binary:"abCD012yz"
+    upcase $S1, $S0
+    pop_eh
+    goto null3
+catch3:
+    .get_results($P9)
+    $S9 = $P9['message']
+    pop_eh
+null3:
+    is ($S9, "Invalid operation on binary string", 'upcase binary')
 .end
 
 .sub test_downcase
diff --git a/t/op/string_cs.t b/t/op/string_cs.t
index 440ee35a35..6861637375 100644
--- a/t/op/string_cs.t
+++ b/t/op/string_cs.t
@@ -5,7 +5,7 @@ use strict;
 use warnings;
 use lib qw( . lib ../lib ../../lib );
 use Test::More;
-use Parrot::Test tests => 57;
+use Parrot::Test tests => 58;
 use Parrot::Config;
 
 =head1 NAME
@@ -388,6 +388,16 @@ CODE
 /Lossy conversion/
 OUTPUT
 
+pasm_error_output_like( <<'CODE', <<OUTPUT, "trans_encoding_s_s_i utf-16 to ucs-2 - lossy" );
+    set S1, utf16:"abc\x{10101}def"
+    find_encoding I0, "ucs2"
+    trans_encoding S2, S1, I0
+    print "never\n"
+    end
+CODE
+/Lossy conversion/
+OUTPUT
+
 pasm_output_is( <<'CODE', <<OUTPUT, "trans_encoding_s_s_i iso-8859-1 to ucs4" );
     set S0, iso-8859-1:"abc_ä_"
     find_encoding I0, "ucs4"
@@ -413,6 +423,8 @@ pasm_output_is( <<'CODE', <<OUTPUT, "trans_encoding_s_s_i utf8 to ucs4" );
     set S0, utf8:"\x{fc}_\x{20202}"
     find_encoding I0, "ucs4"
     trans_encoding S1, S0, I0
+    # also test ucs4 to ucs4 conversion
+    trans_encoding S1, S1, I0
     iseq I1, S0, S1
     print I1
     print "\n"
diff --git a/t/pmc/stringiterator.t b/t/pmc/stringiterator.t
index f0cdcb6100..87502a01bf 100644
--- a/t/pmc/stringiterator.t
+++ b/t/pmc/stringiterator.t
@@ -34,7 +34,7 @@ Tests the C<StringIterator> PMC. Iterate over string in both directions.
     get_keyed(iso-8859-1:"a\x{e4}c\x{f6}e\x{fc}g", utf8:"ä", utf8:"ö", utf8:"ü")
     get_keyed(binary:"a\x{e4}c\x{f6}e\x{fc}g", utf8:"ä", utf8:"ö", utf8:"ü")
     get_keyed(utf8:"aäc\x{20123}eüg", utf8:"ä", utf8:"\x{20123}", utf8:"ü")
-    get_keyed(utf16:"aäcöe\x{20abc}g", utf8:"ä", utf8:"ö", utf8:"\x{20abc}")
+    get_keyed(utf16:"aä\x{20456}öe\x{20abc}g", utf8:"ä", utf8:"ö", utf8:"\x{20abc}")
     get_keyed(ucs2:"aäcöe\x{beef}g", utf8:"ä", utf8:"ö", utf8:"\x{beef}")
     get_keyed(ucs4:"a\x{20789}cöeüg", utf8:"\x{20789}", utf8:"ö", utf8:"ü")