diff --git a/src/Compiler/Symbols/Exprs.fs b/src/Compiler/Symbols/Exprs.fs
index eabc11f3410..6734694d26d 100644
--- a/src/Compiler/Symbols/Exprs.fs
+++ b/src/Compiler/Symbols/Exprs.fs
@@ -1266,7 +1266,7 @@ module FSharpExprConvert =
             let acc = 
                 match dfltOpt with 
                 | Some d -> ConvDecisionTreePrim cenv env dtreeRetTy d 
-                | None -> wfail( "FSharp.Compiler.Service cannot yet return this kind of pattern match", m)
+                | None -> E.DecisionTreeSuccess(0, [])
 
             (csl, acc) ||> List.foldBack (ConvDecisionTreeCase (cenv: SymbolEnv) env m inpExpr dtreeRetTy)
 
diff --git a/tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj b/tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj
index ba862a29ce1..2eb2e1d954a 100644
--- a/tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj
+++ b/tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj
@@ -97,6 +97,7 @@
       <Link>RangeTests.fs</Link>
     </Compile>
     <Compile Include="TooltipTests.fs" />
+    <Compile Include="FSharpExprPatternsTests.fs" />
     <Compile Include="SourceTextTests.fs" />
     <Compile Include="UnnecessaryParenthesesTests.fs" />
     <Compile Include="..\service\Program.fs">
diff --git a/tests/FSharp.Compiler.Service.Tests/FSharpExprPatternsTests.fs b/tests/FSharp.Compiler.Service.Tests/FSharpExprPatternsTests.fs
new file mode 100644
index 00000000000..5d31b6f74fc
--- /dev/null
+++ b/tests/FSharp.Compiler.Service.Tests/FSharpExprPatternsTests.fs
@@ -0,0 +1,173 @@
+module FSharp.Compiler.Service.Tests.FSharpExprPatternsTests
+
+#nowarn "57"
+
+open FSharp.Compiler.CodeAnalysis
+open FSharp.Compiler.Service.Tests.Common
+open FSharp.Compiler.Text
+open FSharp.Compiler.Symbols
+open NUnit.Framework
+
+module TASTCollecting =
+
+    open FSharp.Compiler.Symbols.FSharpExprPatterns
+
+    type Handler = NewUnionCaseHandler of (string -> unit)
+
+    let rec visitExpr (handler: Handler) (e: FSharpExpr) =
+        match e with
+        | AddressOf lvalueExpr -> visitExpr handler lvalueExpr
+        | AddressSet (lvalueExpr, rvalueExpr) ->
+            visitExpr handler lvalueExpr
+            visitExpr handler rvalueExpr
+        | Application (funcExpr, _typeArgs, argExprs) ->
+            visitExpr handler funcExpr
+            visitExprs handler argExprs
+        | Call (objExprOpt, memberOrFunc, _typeArgs1, _typeArgs2, argExprs) ->
+            visitObjArg handler objExprOpt
+            visitExprs handler argExprs
+        | Coerce (_targetType, inpExpr) -> visitExpr handler inpExpr
+        | FastIntegerForLoop (startExpr, limitExpr, consumeExpr, _isUp, _debugPointAtFor, _debugPointAtInOrTo) ->
+            visitExpr handler startExpr
+            visitExpr handler limitExpr
+            visitExpr handler consumeExpr
+        | ILAsm (_asmCode, _typeArgs, argExprs) -> visitExprs handler argExprs
+        | ILFieldGet (objExprOpt, _fieldType, _fieldName) -> visitObjArg handler objExprOpt
+        | ILFieldSet (objExprOpt, _fieldType, _fieldName, _valueExpr) -> visitObjArg handler objExprOpt
+        | IfThenElse (guardExpr, thenExpr, elseExpr) ->
+            visitExpr handler guardExpr
+            visitExpr handler thenExpr
+            visitExpr handler elseExpr
+        | Lambda (_lambdaVar, bodyExpr) -> visitExpr handler bodyExpr
+        | Let ((_bindingVar, bindingExpr, _debugPointAtBinding), bodyExpr) ->
+            visitExpr handler bindingExpr
+            visitExpr handler bodyExpr
+        | LetRec (recursiveBindings, bodyExpr) ->
+            let recursiveBindings' =
+                recursiveBindings |> List.map (fun (mfv, expr, _dp) -> (mfv, expr))
+
+            List.iter (snd >> visitExpr handler) recursiveBindings'
+            visitExpr handler bodyExpr
+        | NewArray (_arrayType, argExprs) -> visitExprs handler argExprs
+        | NewDelegate (_delegateType, delegateBodyExpr) -> visitExpr handler delegateBodyExpr
+        | NewObject (_objType, _typeArgs, argExprs) -> visitExprs handler argExprs
+        | NewRecord (_recordType, argExprs) -> visitExprs handler argExprs
+        | NewTuple (_tupleType, argExprs) -> visitExprs handler argExprs
+        | NewUnionCase (_unionType, unionCase, argExprs) ->
+            match handler with
+            | NewUnionCaseHandler h -> h unionCase.Name
+
+            visitExprs handler argExprs
+        | Quote quotedExpr -> visitExpr handler quotedExpr
+        | FSharpFieldGet (objExprOpt, _recordOrClassType, _fieldInfo) -> visitObjArg handler objExprOpt
+        | FSharpFieldSet (objExprOpt, _recordOrClassType, _fieldInfo, argExpr) ->
+            visitObjArg handler objExprOpt
+            visitExpr handler argExpr
+        | Sequential (firstExpr, secondExpr) ->
+            visitExpr handler firstExpr
+            visitExpr handler secondExpr
+        | TryFinally (bodyExpr, finalizeExpr, _debugPointAtTry, _debugPointAtFinally) ->
+            visitExpr handler bodyExpr
+            visitExpr handler finalizeExpr
+        | TryWith (bodyExpr, _, _, _catchVar, catchExpr, _debugPointAtTry, _debugPointAtWith) ->
+            visitExpr handler bodyExpr
+            visitExpr handler catchExpr
+        | TupleGet (_tupleType, _tupleElemIndex, tupleExpr) -> visitExpr handler tupleExpr
+        | DecisionTree (decisionExpr, decisionTargets) ->
+            visitExpr handler decisionExpr
+            List.iter (snd >> visitExpr handler) decisionTargets
+        | DecisionTreeSuccess (_decisionTargetIdx, decisionTargetExprs) -> visitExprs handler decisionTargetExprs
+        | TypeLambda (_genericParam, bodyExpr) -> visitExpr handler bodyExpr
+        | TypeTest (_ty, inpExpr) -> visitExpr handler inpExpr
+        | UnionCaseSet (unionExpr, _unionType, _unionCase, _unionCaseField, valueExpr) ->
+            visitExpr handler unionExpr
+            visitExpr handler valueExpr
+        | UnionCaseGet (unionExpr, _unionType, _unionCase, _unionCaseField) -> visitExpr handler unionExpr
+        | UnionCaseTest (unionExpr, _unionType, _unionCase) -> visitExpr handler unionExpr
+        | UnionCaseTag (unionExpr, _unionType) -> visitExpr handler unionExpr
+        | ObjectExpr (_objType, baseCallExpr, overrides, interfaceImplementations) ->
+            visitExpr handler baseCallExpr
+            List.iter (visitObjMember handler) overrides
+            List.iter (snd >> List.iter (visitObjMember handler)) interfaceImplementations
+        | TraitCall (_sourceTypes, _traitName, _typeArgs, _typeInstantiation, _argTypes, argExprs) -> visitExprs handler argExprs
+        | ValueSet (_valToSet, valueExpr) -> visitExpr handler valueExpr
+        | WhileLoop (guardExpr, bodyExpr, _debugPointAtWhile) ->
+            visitExpr handler guardExpr
+            visitExpr handler bodyExpr
+        | BaseValue _baseType -> ()
+        | DefaultValue _defaultType -> ()
+        | ThisValue _thisType -> ()
+        | Const (_constValueObj, _constType) -> ()
+        | Value _valueToGet -> ()
+        | CallWithWitnesses (expr, _mfv, _typeLst, _typeLst2, exprs1, exprs2) ->
+            expr |> Option.iter (visitExpr handler)
+            exprs1 |> List.iter (visitExpr handler)
+            exprs2 |> List.iter (visitExpr handler)
+        | NewAnonRecord (_, exprLst) -> exprLst |> List.iter (visitExpr handler)
+        | AnonRecordGet (expr, _, _) -> visitExpr handler expr
+        | DebugPoint (_d, expr) -> visitExpr handler expr
+        | WitnessArg _ -> ()
+        | _ -> ()
+
+    and visitExprs f exprs = List.iter (visitExpr f) exprs
+
+    and visitObjArg f objOpt = Option.iter (visitExpr f) objOpt
+
+    and visitObjMember f memb = visitExpr f memb.Body
+
+    let rec visitDeclaration f d =
+        match d with
+        | FSharpImplementationFileDeclaration.Entity (_e, subDecls) ->
+            for subDecl in subDecls do
+                visitDeclaration f subDecl
+        | FSharpImplementationFileDeclaration.MemberOrFunctionOrValue (_v, _vs, e) -> visitExpr f e
+        | FSharpImplementationFileDeclaration.InitAction e -> visitExpr f e
+
+let testPatterns handler source =
+    let files = Map.ofArray [| "A.fs", SourceText.ofString source |]
+
+    let documentSource fileName =
+        Map.tryFind fileName files |> async.Return
+
+    let projectOptions =
+        let _, projectOptions = mkTestFileAndOptions "" Array.empty
+
+        { projectOptions with
+            SourceFiles = [| "A.fs" |]
+        }
+
+    let checker =
+        FSharpChecker.Create(documentSource = DocumentSource.Custom documentSource, keepAssemblyContents = true)
+
+    let checkResult =
+        checker.ParseAndCheckFileInProject("A.fs", 0, Map.find "A.fs" files, projectOptions)
+        |> Async.RunImmediate
+
+    match checkResult with
+    | _, FSharpCheckFileAnswer.Succeeded (checkResults) ->
+
+        match checkResults.ImplementationFile with
+        | Some implFile ->
+            for decl in implFile.Declarations do
+                TASTCollecting.visitDeclaration handler decl
+        | _ -> ()
+    | _, _ -> ()
+
+[<Test>]
+let ``union case with type`` () =
+    let implSource =
+        """
+module M
+
+type T = Case1 of string
+
+let x = Case1 "bla" 
+"""
+
+    let lst = ResizeArray<string>()
+
+    let handler: TASTCollecting.Handler =
+        TASTCollecting.Handler.NewUnionCaseHandler lst.Add
+
+    Assert.DoesNotThrow(fun _ -> testPatterns handler implSource)
+    Assert.Contains("Case1", lst)