diff --git a/src/fsharp/IlxGen.fs b/src/fsharp/IlxGen.fs
index 4dca4fc4ada..f8252601a13 100644
--- a/src/fsharp/IlxGen.fs
+++ b/src/fsharp/IlxGen.fs
@@ -3080,20 +3080,20 @@ and GenUntupledArgsDiscardingLoneUnit cenv cgbuf eenv m numObjArgs curriedArgInf
         GenExpr cenv cgbuf eenv SPSuppress arg2 discard
     | _ ->
         (curriedArgInfos, args) ||> List.iter2 (fun argInfos x ->
-            GenUntupledArgExpr cenv cgbuf eenv m argInfos x Continue)
+            GenUntupledArgExpr cenv cgbuf eenv m argInfos x)
 
 /// Codegen arguments
-and GenUntupledArgExpr cenv cgbuf eenv m argInfos expr sequel =
+and GenUntupledArgExpr cenv cgbuf eenv m argInfos expr =
     let g = cenv.g
     let numRequiredExprs = List.length argInfos
-    assert (numRequiredExprs >= 1)
-    if numRequiredExprs = 1 then
-        GenExpr cenv cgbuf eenv SPSuppress expr sequel
+    if numRequiredExprs = 0 then
+        ()
+    elif numRequiredExprs = 1 then
+        GenExpr cenv cgbuf eenv SPSuppress expr Continue
     elif isRefTupleExpr expr then
         let es = tryDestRefTupleExpr expr
         if es.Length <> numRequiredExprs then error(InternalError("GenUntupledArgExpr (2)", m))
         es |> List.iter (fun x -> GenExpr cenv cgbuf eenv SPSuppress x Continue)
-        GenSequel cenv eenv.cloc cgbuf sequel
     else
         let ty = tyOfExpr g expr
         let locv, loce = mkCompGenLocal m "arg" ty
@@ -3104,7 +3104,6 @@ and GenUntupledArgExpr cenv cgbuf eenv m argInfos expr sequel =
             let tys = destRefTupleTy g ty
             assert (tys.Length = numRequiredExprs)
             argInfos |> List.iteri (fun i _ -> GenGetTupleField cenv cgbuf eenvinner (tupInfoRef, loce, tys, i, m) Continue)
-            GenSequel cenv eenv.cloc cgbuf sequel
         )
 
 
@@ -3224,7 +3223,7 @@ and GenApp (cenv: cenv) cgbuf eenv (f, fty, tyargs, curriedArgs, m) sequel =
                     // static extension method with empty arguments. 
                     | [[]], [_] when numObjArgs = 0 -> 0
                     // instance extension method with empty arguments. 
-                    | [[_];[]], [_;_] when numObjArgs = 1 -> 0
+                    | [[_];[]], [_;_] when numObjArgs = 0 -> 1
                     | _ -> numMethodArgs
                 else numMethodArgs
 
diff --git a/tests/fsharp/tests.fs b/tests/fsharp/tests.fs
index a7e6fdfa37b..65d146cc581 100644
--- a/tests/fsharp/tests.fs
+++ b/tests/fsharp/tests.fs
@@ -2251,6 +2251,12 @@ module TypecheckTests =
         peverify cfg "pos36-srtp-app.exe"
         exec cfg ("." ++ "pos36-srtp-app.exe") ""
 
+    [<Test>]
+    let ``sigs pos38`` () =
+        let cfg = testConfig' "typecheck/sigs"
+        fsc cfg "%s --target:library -o:pos38.dll --warnaserror" cfg.fsc_flags ["pos38.fs"]
+        peverify cfg "pos38.dll"
+
     [<Test>]
     let ``sigs pos23`` () =
         let cfg = testConfig' "typecheck/sigs"
diff --git a/tests/fsharp/typecheck/sigs/pos38.fs b/tests/fsharp/typecheck/sigs/pos38.fs
new file mode 100644
index 00000000000..bf9ad7ea8f9
--- /dev/null
+++ b/tests/fsharp/typecheck/sigs/pos38.fs
@@ -0,0 +1,28 @@
+module Pos38
+
+type Expression =
+    | EndOp
+    | BinaryOp of Expression * Expression
+
+let mutable count = 0
+
+[<AutoOpen>]
+module Extensions =
+
+    type Expression with
+
+        member this.Foobar2 : unit =
+            match this with
+            | BinaryOp (_, e2) ->
+                e2.Foobar2
+            | EndOp -> 
+                count <- count + 1
+                ()
+
+
+let c = BinaryOp(EndOp, EndOp)
+
+c.Foobar2
+
+if count <> 1 then failwith "incorrect count"
+