diff --git a/CONTRIBUTORS.markdown b/CONTRIBUTORS.markdown
index e35d40033b..413ef3da70 100644
--- a/CONTRIBUTORS.markdown
+++ b/CONTRIBUTORS.markdown
@@ -88,3 +88,4 @@ The format for this list: name, GitHub handle
 * Eric Torreborre (@etorreborre)
 * Eduard Nicodei (@neduard)
 * Brian McKenna (@puffnfresh)
+* Ruslan Simchuk (@SimaDovakin)
diff --git a/editor-support/vim/syntax/unison.vim b/editor-support/vim/syntax/unison.vim
index ec193723a7..3bd3b2ef68 100644
--- a/editor-support/vim/syntax/unison.vim
+++ b/editor-support/vim/syntax/unison.vim
@@ -48,7 +48,7 @@ syn match   uSpecialCharError	contained "\\&\|'''\+"
 syn region  uString		start=+"+  skip=+\\\\\|\\"+  end=+"+  contains=uSpecialChar
 syn match   uCharacter		"[^a-zA-Z0-9_']'\([^\\]\|\\[^']\+\|\\'\)'"lc=1 contains=uSpecialChar,uSpecialCharError
 syn match   uCharacter		"^'\([^\\]\|\\[^']\+\|\\'\)'" contains=uSpecialChar,uSpecialCharError
-syn match   uNumber		"\<[0-9]\+\>\|\<0[xX][0-9a-fA-F]\+\>\|\<0[oO][0-7]\+\>"
+syn match   uNumber		"\<[0-9]\+\>\|\<0[xX][0-9a-fA-F]\+\>\|\<0[oO][0-7]\+\>\|\<0[bB][01]\+\>"
 syn match   uFloat		"\<[0-9]\+\.[0-9]\+\([eE][-+]\=[0-9]\+\)\=\>"
 
 " Keyword definitions. These must be patterns instead of keywords
@@ -83,7 +83,7 @@ syn region  uDocDirective     contained matchgroup=unisonDocDirective start="\(@
 
 syn match uDebug "\<\(todo\|bug\|Debug.trace\)\>"
 
-" things like 
+" things like
 "    > my_func 1 3
 "    test> Function.tap.tests.t1 = check let
 "      use Nat == +
@@ -101,7 +101,7 @@ if version >= 508 || !exists("did_u_syntax_inits")
   else
     command -nargs=+ HiLink hi def link <args>
   endif
-   
+
    HiLink       uWatch                           Debug
    HiLink       uDocMono                         Delimiter
    HiLink       unisonDocDirective               Import
diff --git a/parser-typechecker/src/Unison/PrintError.hs b/parser-typechecker/src/Unison/PrintError.hs
index a4cf9e4b25..d39e152903 100644
--- a/parser-typechecker/src/Unison/PrintError.hs
+++ b/parser-typechecker/src/Unison/PrintError.hs
@@ -1428,6 +1428,18 @@ renderParseErrors s = \case
                   <> "after the"
                   <> Pr.group (style ErrorSite "0o" <> ".")
             ]
+        L.InvalidBinaryLiteral ->
+          Pr.lines
+            [ "This number isn't valid syntax: ",
+              "",
+              excerpt,
+              Pr.wrap $
+                "I was expecting only binary characters"
+                  <> "(one of"
+                  <> Pr.group (style Code "01" <> ")")
+                  <> "after the"
+                  <> Pr.group (style ErrorSite "0b" <> ".")
+            ]
         L.InvalidShortHash h ->
           Pr.lines
             [ "Invalid hash: " <> style ErrorSite (fromString h),
diff --git a/unison-src/transcripts/error-messages.md b/unison-src/transcripts/error-messages.md
index 8490e491a2..f3b0353806 100644
--- a/unison-src/transcripts/error-messages.md
+++ b/unison-src/transcripts/error-messages.md
@@ -27,7 +27,7 @@ x = 1e- -- missing an exponent
 x = 1E+ -- missing an exponent
 ```
 
-### Hex, octal, and bytes literals
+### Hex, octal, binary, and bytes literals
 
 ```unison:error
 x = 0xoogabooga -- invalid hex chars
@@ -37,6 +37,10 @@ x = 0xoogabooga -- invalid hex chars
 x = 0o987654321 -- 9 and 8 are not valid octal char
 ```
 
+```unison:error
+x = 0b3201 -- 3 and 2 are not valid binary chars
+```
+
 ```unison:error
 x = 0xsf -- odd number of hex chars in a bytes literal
 ```
@@ -81,7 +85,7 @@ foo = cases
 ```unison:error
 -- Missing a '->'
 x = match Some a with
-      None -> 
+      None ->
         1
       Some _
         2
diff --git a/unison-src/transcripts/error-messages.output.md b/unison-src/transcripts/error-messages.output.md
index 148218a759..ebcce29e97 100644
--- a/unison-src/transcripts/error-messages.output.md
+++ b/unison-src/transcripts/error-messages.output.md
@@ -70,7 +70,7 @@ x = 1E+ -- missing an exponent
   `1e+37`.
 
 ```
-### Hex, octal, and bytes literals
+### Hex, octal, binary, and bytes literals
 
 ``` unison
 x = 0xoogabooga -- invalid hex chars
@@ -103,6 +103,22 @@ x = 0o987654321 -- 9 and 8 are not valid octal char
   I was expecting only octal characters (one of 01234567) after
   the 0o.
 
+```
+``` unison
+x = 0b3201 -- 3 and 2 are not valid binary chars
+```
+
+``` ucm
+
+  Loading changes detected in scratch.u.
+
+  This number isn't valid syntax: 
+  
+      1 | x = 0b3201 -- 3 and 2 are not valid binary chars
+  
+  I was expecting only binary characters (one of 01) after the
+  0b.
+
 ```
 ``` unison
 x = 0xsf -- odd number of hex chars in a bytes literal
@@ -244,7 +260,7 @@ foo = cases
 ``` unison
 -- Missing a '->'
 x = match Some a with
-      None -> 
+      None ->
         1
       Some _
         2
diff --git a/unison-syntax/src/Unison/Syntax/Lexer/Unison.hs b/unison-syntax/src/Unison/Syntax/Lexer/Unison.hs
index ac31fdcac4..7db46e5bd6 100644
--- a/unison-syntax/src/Unison/Syntax/Lexer/Unison.hs
+++ b/unison-syntax/src/Unison/Syntax/Lexer/Unison.hs
@@ -87,6 +87,7 @@ data Err
   | InvalidBytesLiteral String
   | InvalidHexLiteral
   | InvalidOctalLiteral
+  | InvalidBinaryLiteral
   | Both Err Err
   | MissingFractional String -- ex `1.` rather than `1.04`
   | MissingExponent String -- ex `1e` rather than `1e3`
@@ -535,7 +536,7 @@ lexemes eof =
           case Bytes.fromBase16 $ Bytes.fromWord8s (fromIntegral . ord <$> s) of
             Left _ -> err start (InvalidBytesLiteral $ "0xs" <> s)
             Right bs -> pure (Bytes bs)
-        otherbase = octal <|> hex
+        otherbase = octal <|> hex <|> binary
         octal = do
           start <- posP
           commitAfter2 sign (lit "0o") $ \sign _ ->
@@ -544,6 +545,10 @@ lexemes eof =
           start <- posP
           commitAfter2 sign (lit "0x") $ \sign _ ->
             fmap (num sign) LP.hexadecimal <|> err start InvalidHexLiteral
+        binary = do
+          start <- posP
+          commitAfter2 sign (lit "0b") $ \sign _ ->
+            fmap (num sign) LP.binary <|> err start InvalidBinaryLiteral
 
         num :: Maybe String -> Integer -> Lexeme
         num sign n = Numeric (fromMaybe "" sign <> show n)