diff --git a/py/lexer.c b/py/lexer.c
index 536208e..12cb5ae 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -261,16 +261,6 @@
     "__debug__",
 };
 
-STATIC mp_uint_t hex_digit(unichar c) {
-    // c is assumed to be hex digit
-    mp_uint_t n = c - '0';
-    if (n > 9) {
-        n &= ~('a' - 'A');
-        n -= ('A' - ('9' + 1));
-    }
-    return n;
-}
-
 // This is called with CUR_CHAR() before first hex digit, and should return with
 // it pointing to last hex digit
 // num_digits must be greater than zero
@@ -282,7 +272,7 @@
         if (!unichar_isxdigit(c)) {
             return false;
         }
-        num = (num << 4) + hex_digit(c);
+        num = (num << 4) + unichar_xdigit_value(c);
     }
     *result = num;
     return true;
diff --git a/py/misc.h b/py/misc.h
index 2c00b68..91bd000 100644
--- a/py/misc.h
+++ b/py/misc.h
@@ -127,6 +127,7 @@
 bool unichar_islower(unichar c);
 unichar unichar_tolower(unichar c);
 unichar unichar_toupper(unichar c);
+mp_uint_t unichar_xdigit_value(unichar c);
 mp_uint_t unichar_charlen(const char *str, mp_uint_t len);
 #define UTF8_IS_NONASCII(ch) ((ch) & 0x80)
 #define UTF8_IS_CONT(ch) (((ch) & 0xC0) == 0x80)
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index 5d0dc9d..a5e543b 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -584,6 +584,7 @@
 #if MICROPY_PY_UBINASCII
 Q(ubinascii)
 Q(hexlify)
+Q(unhexlify)
 #endif
 
 #if MICROPY_PY_MACHINE
diff --git a/py/unicode.c b/py/unicode.c
index db4aa43..63e9601 100644
--- a/py/unicode.c
+++ b/py/unicode.c
@@ -169,3 +169,13 @@
     }
     return c;
 }
+
+mp_uint_t unichar_xdigit_value(unichar c) {
+    // c is assumed to be hex digit
+    mp_uint_t n = c - '0';
+    if (n > 9) {
+        n &= ~('a' - 'A');
+        n -= ('A' - ('9' + 1));
+    }
+    return n;
+}