diff --git a/py/objstr.c b/py/objstr.c
index c7e4ebf53b..a51be74747 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -743,11 +743,29 @@ static mp_obj_t str_finder(size_t n_args, const mp_obj_t *args, int direction, b
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
     check_is_str_or_bytes(args[0]);
 
-    // check argument type
-    str_check_arg_type(self_type, args[1]);
-
     GET_STR_DATA_LEN(args[0], haystack, haystack_len);
-    GET_STR_DATA_LEN(args[1], needle, needle_len);
+
+    mp_int_t val;
+    byte needle_data;
+    const byte *needle;
+    size_t needle_len;
+    if (self_type != &mp_type_str && mp_obj_get_int_maybe(args[1], &val)) {
+        // Allow {bytes/bytearray}.{find,index}(int).
+        #if MICROPY_FULL_CHECKS
+        if (val < 0 || val > 255) {
+            mp_raise_ValueError(MP_ERROR_TEXT("bytes value out of range"));
+        }
+        #endif
+        needle_data = val;
+        needle = &needle_data;
+        needle_len = 1;
+    } else {
+        // check argument type
+        str_check_arg_type(self_type, args[1]);
+        GET_STR_DATA_LEN(args[1], needle_tmp, needle_len_tmp);
+        needle = needle_tmp;
+        needle_len = needle_len_tmp;
+    }
 
     const byte *start = haystack;
     const byte *end = haystack + haystack_len;
diff --git a/tests/basics/bytearray_byte_operations.py b/tests/basics/bytearray_byte_operations.py
index 48b08ab261..794fe8cafa 100644
--- a/tests/basics/bytearray_byte_operations.py
+++ b/tests/basics/bytearray_byte_operations.py
@@ -2,6 +2,7 @@
 
 print(bytearray(b"hello world").find(b"ll"))
 print(bytearray(b"hello\x00world").rfind(b"l"))
+print(bytearray(b"hello world").find(ord(b"l")))
 
 print(bytearray(b"abc  efg ").strip(b"g a"))
 print(bytearray(b"   spacious   ").lstrip())
@@ -14,10 +15,18 @@ print(bytearray(b"abcabc").rsplit(b"bc"))
 
 print(bytearray(b"asdfasdf").replace(b"a", b"b"))
 
-print("00\x0000".index("0", 0))
-print("00\x0000".index("0", 3))
-print("00\x0000".rindex("0", 0))
-print("00\x0000".rindex("0", 3))
+print(b"00\x0000".index(b"0", 0))
+print(b"00\x0000".index(b"0", 3))
+print(b"00\x0000".index(ord("0"), 0))
+print(b"00\x0000".index(ord("0"), 3))
+print(b"00\x0000".index(0, 0))
+try:
+    print(b"00\x0000".index(0, 3))
+except ValueError:
+    print("ValueError")
+print(b"00\x0000".index(b"0", 3))
+print(b"00\x0000".rindex(b"0", 0))
+print(b"00\x0000".rindex(b"0", 3))
 
 print(bytearray(b"foobar").endswith(b"bar"))
 print(bytearray(b"1foo").startswith(b"foo", 1))
diff --git a/tests/basics/bytes_find.py b/tests/basics/bytes_find.py
index 75ef9796cd..4a2707cc53 100644
--- a/tests/basics/bytes_find.py
+++ b/tests/basics/bytes_find.py
@@ -21,6 +21,34 @@ print(b"0000".find(b'-1', 3))
 print(b"0000".find(b'1', 3))
 print(b"0000".find(b'1', 4))
 print(b"0000".find(b'1', 5))
+print(b"0000".find(ord(b'0')))
+print(b"0000".find(ord(b'0'), 0))
+print(b"0000".find(ord(b'0'), 1))
+print(b"0000".find(ord(b'0'), 2))
+print(b"0000".find(ord(b'0'), 3))
+print(b"0000".find(ord(b'0'), 4))
+print(b"0000".find(ord(b'0'), 5))
+print(b"0000".find(ord(b'x'), 3))
+print(b"0000".find(ord(b'1'), 3))
+print(b"0000".find(ord(b'1'), 4))
+print(b"0000".find(ord(b'1'), 5))
 
 # Non-ascii values (make sure not treated as unicode-like)
 print(b"\x80abc".find(b"a", 1))
+
+# Int-like conversion.
+print(b"00\x0000".find(b'0', True))
+
+# Out of bounds int.
+try:
+    print(b"0000".find(b'0', -1))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".find(b'0', 256))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".find(b'0', 91273611))
+except ValueError:
+    print("ValueError")
diff --git a/tests/basics/bytes_index.py b/tests/basics/bytes_index.py
new file mode 100644
index 0000000000..08ed46e4a9
--- /dev/null
+++ b/tests/basics/bytes_index.py
@@ -0,0 +1,99 @@
+print(b"hello world".index(b"ll"))
+print(b"hello world".index(b"ll", None))
+print(b"hello world".index(b"ll", 1))
+print(b"hello world".index(b"ll", 1, None))
+print(b"hello world".index(b"ll", None, None))
+print(b"hello world".index(b"ll", 1, -1))
+try:
+    print(b"hello world".index(b"ll", 1, 1))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"hello world".index(b"ll", 1, 2))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"hello world".index(b"ll", 1, 3))
+except ValueError:
+    print("ValueError")
+print(b"hello world".index(b"ll", 1, 4))
+print(b"hello world".index(b"ll", 1, 5))
+print(b"hello world".index(b"ll", -100))
+print(b"0000".index(b'0'))
+print(b"0000".index(b'0', 0))
+print(b"0000".index(b'0', 1))
+print(b"0000".index(b'0', 2))
+print(b"0000".index(b'0', 3))
+try:
+    print(b"0000".index(b'0', 4))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'0', 5))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'-1', 3))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'1', 3))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'1', 4))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'1', 5))
+except ValueError:
+    print("ValueError")
+print(b"0000".index(ord(b'0')))
+print(b"0000".index(ord(b'0'), 0))
+print(b"0000".index(ord(b'0'), 1))
+print(b"0000".index(ord(b'0'), 2))
+print(b"0000".index(ord(b'0'), 3))
+try:
+    print(b"0000".index(ord(b'0'), 4))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(ord(b'0'), 5))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(ord(b'x'), 3))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(ord(b'1'), 3))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(ord(b'1'), 4))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(ord(b'1'), 5))
+except ValueError:
+    print("ValueError")
+
+# Non-ascii values (make sure not treated as unicode-like)
+print(b"\x80abc".index(b"a", 1))
+
+# Int-like conversion.
+print(b"00\x0000".index(b'0', True))
+
+# Out of bounds int.
+try:
+    print(b"0000".index(b'0', -1))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'0', 256))
+except ValueError:
+    print("ValueError")
+try:
+    print(b"0000".index(b'0', 91273611))
+except ValueError:
+    print("ValueError")
diff --git a/tests/basics/string_find.py b/tests/basics/string_find.py
index f9fcad3e57..f37064ad29 100644
--- a/tests/basics/string_find.py
+++ b/tests/basics/string_find.py
@@ -24,6 +24,7 @@ print("0000".find('1', 5))
 print("aaaaaaaaaaa".find("bbb", 9, 2))
 
 try:
+    # Only works on bytes/bytearray.
     'abc'.find(1)
 except TypeError:
     print('TypeError')
diff --git a/tests/basics/string_index.py b/tests/basics/string_index.py
index 31f6900e6c..328f2dff54 100644
--- a/tests/basics/string_index.py
+++ b/tests/basics/string_index.py
@@ -76,3 +76,9 @@ except ValueError:
     print("Raised ValueError")
 else:
     print("Did not raise ValueError")
+
+try:
+    # Only works on bytes/bytearray.
+    'abc'.index(1)
+except TypeError:
+    print('TypeError')