diff --git a/json5/json5.g b/json5/json5.g
index 7cafff3..2e00636 100644
--- a/json5/json5.g
+++ b/json5/json5.g
@@ -118,7 +118,7 @@ id_esc_continue = id_esc_start
                 | ~~('u' ('200C' | '200c' | '200D' | '200d')) unicode_esc
 
 num_literal    = '-' unsigned_lit:n                  -> '-' + n
-               | '+' unsigned_lit:n                  -> n
+               | '+' unsigned_lit:n                  -> '+' + n
                | unsigned_lit:n                      -> n
 
 unsigned_lit   = dec_literal:d ~id_start             -> d
diff --git a/json5/lib.py b/json5/lib.py
index 91c2b46..9c76355 100644
--- a/json5/lib.py
+++ b/json5/lib.py
@@ -372,7 +372,7 @@ def _fp_constant_parser(s):
         return float(s.replace('Infinity', 'inf').replace('NaN', 'nan'))
 
     def _parse_int(s):
-        if s.lstrip('-').startswith(('0x', '0X')):
+        if s.lstrip('+-').startswith(('0x', '0X')):
             return int(s, 16)
         return int(s)
 
@@ -414,7 +414,7 @@ def _walk_ast(
         return False
     ty, v = el
     if ty == 'number':
-        unsigned = v[1:] if v.startswith('-') else v
+        unsigned = v[1:] if v[:1] in ('-', '+') else v
         if unsigned.startswith(('0x', '0X')):
             return parse_int(v)
         if '.' in v or 'e' in v or 'E' in v:
diff --git a/json5/parser.py b/json5/parser.py
index ab5deb7..dd6275f 100644
--- a/json5/parser.py
+++ b/json5/parser.py
@@ -1423,7 +1423,7 @@ def _num_literal__c1_(self):
             [
                 lambda: self._ch('+'),
                 lambda: self._bind(self._unsigned_lit_, 'n'),
-                lambda: self._succeed(self._get('n')),
+                lambda: self._succeed('+' + self._get('n')),
             ]
         )
         self._pop('num_literal__c1')
diff --git a/tests/lib_test.py b/tests/lib_test.py
index 161928a..6379510 100644
--- a/tests/lib_test.py
+++ b/tests/lib_test.py
@@ -324,12 +324,17 @@ def hook(x):
             json5.loads('-Infinity', parse_constant=hook), '-Infinity'
         )
         self.assertEqual(json5.loads('NaN', parse_constant=hook), 'NaN')
+        self.assertEqual(
+            json5.loads('+Infinity', parse_constant=hook), '+Infinity'
+        )
+        self.assertEqual(json5.loads('+NaN', parse_constant=hook), '+NaN')
 
     def test_parse_float(self):
         def hook(x):
             return x
 
         self.assertEqual(json5.loads('1.0', parse_float=hook), '1.0')
+        self.assertEqual(json5.loads('+1.5', parse_float=hook), '+1.5')
         for text in ('1E5', '1E+5', '2.5E-3', '1e5', '1e-5'):
             with self.subTest(text=text):
                 self.assertEqual(json5.loads(text, parse_float=hook), text)
@@ -341,8 +346,11 @@ def hook(x):
         self.assertEqual(json5.loads('1', parse_int=hook), '1')
         self.assertEqual(json5.loads('0x10', parse_int=hook), '0x10')
         self.assertEqual(json5.loads('-0xff', parse_int=hook), '-0xff')
+        self.assertEqual(json5.loads('+5', parse_int=hook), '+5')
+        self.assertEqual(json5.loads('+0xff', parse_int=hook), '+0xff')
         self.assertEqual(json5.loads('0x10'), 16)
         self.assertEqual(json5.loads('-0xff'), -255)
+        self.assertEqual(json5.loads('+0xff'), 255)
         self.assertEqual(json5.loads('0X2a'), 42)
 
     def test_sample_file(self):