diff --git a/Differences.md b/Differences.md
index b72e436..f212f9d 100644
--- a/Differences.md
+++ b/Differences.md
@@ -24,7 +24,7 @@ Known issues are essentially bugs, misfeatures, and omissions considered such, a
 
 1. Some functions don't perform argument checking well enough, which potentially may lead to crash if wrong argument types are passed.
 1. Some functions use ``assert()`` for argument checking, which will lead to crash if wrong argument types are passed/erroneous conditions are faced. This should be replaced with Python exception raising.
-1. It's not possible to override builtin functions in a general way. So far - no "builtins" module is implemented, so any overrides work within a current module only.
+1. It's not possible to override builtin functions in a general way. So far - no "builtins" module is implemented, so any overrides work within a current module only. [#959](//github.com/micropython/micropython/issues/959)
 1. There's no support for persistent bytecode, and running bytecode (vs running Python source). [#222](//github.com/micropython/micropython/issues/222)
 1. <strike>print() function doesn't use the Python stream infrastructure, it uses the underlying C printf() function directly. This means if you override sys.stdout, then print() won't be affected. </strike>[#209](//github.com/micropython/micropython/issues/209)
 1. Currently, it's not possible to override sys.stdin, sys.stdout, sys.stderr (for efficiency, they are stored in read-only memory).
@@ -41,4 +41,4 @@ Known issues are essentially bugs, misfeatures, and omissions considered such, a
 1. 3-argument slicing is only partially implemented.
 1. <strike>Keyword and keyword-only arguments need more work</strike> [#466](https://github.com/micropython/micropython/issues/466), [#524](//github.com/micropython/micropython/issues/524).
 1. Only basic support for ``__new__`` method is available [#606](//github.com/micropython/micropython/issues/606), [#622](//github.com/micropython/micropython/issues/622).
-1. Bitwise operations on long ints are only partially implemented (x & 0xffffffff idiom for casting signed 32-bit value to unsigned works).
+1. Bitwise operations on long ints are only partially implemented (x & 0xffffffff idiom for casting signed 32-bit value to unsigned works).
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