diff --git a/src/Fantomas.Tests/Fantomas.Tests.fsproj b/src/Fantomas.Tests/Fantomas.Tests.fsproj
index 13231ce5b5..afb8146c50 100644
--- a/src/Fantomas.Tests/Fantomas.Tests.fsproj
+++ b/src/Fantomas.Tests/Fantomas.Tests.fsproj
@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Version>2.9.1</Version>
     <NoWarn>FS0988</NoWarn>
@@ -44,6 +44,7 @@
     <Compile Include="LazyTests.fs" />
     <Compile Include="LongIdentWithDotsTests.fs" />
     <Compile Include="DynamicOperatorTests.fs" />
+    <Compile Include="SynExprSetTests.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Fantomas\Fantomas.fsproj" />
diff --git a/src/Fantomas.Tests/FormattingPropertyTests.fs b/src/Fantomas.Tests/FormattingPropertyTests.fs
index 6174fa38fd..2c5df1b86e 100644
--- a/src/Fantomas.Tests/FormattingPropertyTests.fs
+++ b/src/Fantomas.Tests/FormattingPropertyTests.fs
@@ -366,6 +366,7 @@ let rec shrinkSynExpr = function
     | SynExpr.DotIndexedGet(expr, _, _, _)
     | SynExpr.DotGet(expr, _, _, _)
     | SynExpr.DotSet(expr, _, _, _)
+    | SynExpr.Set(expr, _, _)
     | SynExpr.TypeTest(expr, _, _)
     | SynExpr.Upcast(expr, _, _)
     | SynExpr.Downcast(expr, _, _)
diff --git a/src/Fantomas.Tests/SynExprSetTests.fs b/src/Fantomas.Tests/SynExprSetTests.fs
new file mode 100644
index 0000000000..7b533569fe
--- /dev/null
+++ b/src/Fantomas.Tests/SynExprSetTests.fs
@@ -0,0 +1,46 @@
+module Fantomas.Tests.SynExprSetTests
+
+open NUnit.Framework
+open FsUnit
+open Fantomas.Tests.TestHelper
+
+/// See https://github.com/fsharp/fsharp/blob/master/src/fsharp/ast.fs#L633
+/// F# syntax: expr <- expr
+/// | Set of SynExpr * SynExpr * range:range
+
+[<Test>]
+let ``array indexer set`` () =
+    formatSourceString false """
+let arr = [|0|]
+(arr.[0]) <- 1
+"""  config
+    |> should equal """let arr = [| 0 |]
+
+(arr.[0]) <- 1
+"""
+
+[<Test>]
+let ``setter of type set`` () =
+    formatSourceString false """
+type T() =
+    member val X = 0 with get, set
+(T().X) <- 1
+"""  config
+    |> prepend newline
+    |> should equal """
+type T() =
+    member val X = 0 with get, set
+
+(T().X) <- 1
+"""
+
+[<Test>]
+let ``mutable value set`` () =
+    formatSourceString false """
+let mutable x = 0
+(x) <- 1
+"""  config
+    |> should equal """let mutable x = 0
+
+(x) <- 1
+"""
diff --git a/src/Fantomas/CodeFormatterImpl.fs b/src/Fantomas/CodeFormatterImpl.fs
index e3302b0421..3106a14dde 100644
--- a/src/Fantomas/CodeFormatterImpl.fs
+++ b/src/Fantomas/CodeFormatterImpl.fs
@@ -233,7 +233,8 @@ let isValidAST ast =
         | SynExpr.DotGet(synExpr, _dotm, _longIdent, _range) -> 
             validateExpr synExpr
 
-        | SynExpr.DotSet(synExpr1, _longIdent, synExpr2, _range) ->
+        | SynExpr.DotSet(synExpr1, _, synExpr2, _)
+        | SynExpr.Set (synExpr1, synExpr2, _) ->
             List.forall validateExpr [synExpr1; synExpr2]
 
         | SynExpr.DotIndexedGet(synExpr, IndexerArgList synExprList, _range, _range2) -> 
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index fb111a6637..e7d4cd966e 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -101,7 +101,8 @@ and genSigModuleOrNamespace astContext (SigModuleOrNamespace(ats, px, ao, s, mds
                 +> opt sepSpace ao genAccess -- s +> rep 2 sepNln)
     +> genSigModuleDeclList astContext mds
 
-and genModuleDeclList astContext = function
+and genModuleDeclList astContext e =
+    match e with
     | [x] -> genModuleDecl astContext x
 
     | OpenL(xs, ys) ->
@@ -713,6 +714,10 @@ and genExpr astContext synExpr =
         let exprF = genExpr { astContext with IsInsideDotGet = true }
         addParenIfAutoNln e exprF -- (sprintf ".%s" s)
     | DotSet(e1, s, e2) -> addParenIfAutoNln e1 (genExpr astContext) -- sprintf ".%s <- " s +> genExpr astContext e2
+
+    | SynExpr.Set(e1,e2, _) ->
+        addParenIfAutoNln e1 (genExpr astContext) -- sprintf " <- " +> genExpr astContext e2
+        
     | LetOrUseBang(isUse, p, e1, e2) ->
         atCurrentColumn (ifElse isUse (!- "use! ") (!- "let! ") 
             +> genPat astContext p -- " = " +> genExpr astContext e1 +> sepNln +> genExpr astContext e2)