diff --git a/stdlib/3/builtins.pyi b/stdlib/3/builtins.pyi
index 58ab271d1..db7e8e2bf 100644
--- a/stdlib/3/builtins.pyi
+++ b/stdlib/3/builtins.pyi
@@ -504,7 +504,10 @@ class bytearray(MutableSequence[int], ByteString):
     def endswith(self, __suffix: Union[bytes, Tuple[bytes, ...]]) -> bool: ...
     def expandtabs(self, tabsize: int = ...) -> bytearray: ...
     def find(self, __sub: Union[bytes, int], __start: Optional[int] = ..., __end: Optional[int] = ...) -> int: ...
-    def hex(self) -> str: ...
+    if sys.version_info >= (3, 8):
+        def hex(self, sep: Union[str, bytes] = ..., bytes_per_sep: int = ...) -> str: ...
+    else:
+        def hex(self) -> str: ...
     def index(self, __sub: Union[bytes, int], __start: Optional[int] = ..., __end: Optional[int] = ...) -> int: ...
     def insert(self, __index: int, __item: int) -> None: ...
     def isalnum(self) -> bool: ...
@@ -618,7 +621,10 @@ class memoryview(Sized, Container[int]):
     if sys.version_info >= (3, 8):
         def toreadonly(self) -> memoryview: ...
     def release(self) -> None: ...
-    def hex(self) -> str: ...
+    if sys.version_info >= (3, 8):
+        def hex(self, sep: Union[str, bytes] = ..., bytes_per_sep: int = ...) -> str: ...
+    else:
+        def hex(self) -> str: ...
 
 class bool(int):
     def __new__(cls: Type[_T], __o: object = ...) -> _T: ...