diff --git a/src/Compiler/Utilities/illib.fs b/src/Compiler/Utilities/illib.fs
index fe091c640b3..4ed4cf57e50 100644
--- a/src/Compiler/Utilities/illib.fs
+++ b/src/Compiler/Utilities/illib.fs
@@ -15,8 +15,6 @@ open FSharp.Compiler.Caches
 
 [<Class>]
 type InterruptibleLazy<'T> private (value, valueFactory: unit -> 'T) =
-    let syncObj = obj ()
-
     [<VolatileField>]
     // TODO nullness - this is boxed to obj because of an attribute targets bug fixed in main, but not yet shipped (needs shipped 8.0.400)
     let mutable valueFactory: objnull = valueFactory
@@ -34,7 +32,7 @@ type InterruptibleLazy<'T> private (value, valueFactory: unit -> 'T) =
         match valueFactory with
         | null -> value
         | _ ->
-            Monitor.Enter(syncObj)
+            Monitor.Enter(this)
 
             try
                 match valueFactory with
@@ -44,7 +42,7 @@ type InterruptibleLazy<'T> private (value, valueFactory: unit -> 'T) =
                     value <- (valueFactory |> unbox<unit -> 'T>) ()
                     valueFactory <- Unchecked.defaultof<_>
             finally
-                Monitor.Exit(syncObj)
+                Monitor.Exit(this)
 
             value
 
@@ -153,8 +151,6 @@ module internal PervasiveAutoOpens =
 
 [<AbstractClass>]
 type DelayInitArrayMap<'T, 'TDictKey, 'TDictValue>(f: unit -> 'T[]) =
-    let syncObj = obj ()
-
     let mutable arrayStore: (_ array | null) = null
     let mutable dictStore: (_ | null) = null
 
@@ -164,7 +160,7 @@ type DelayInitArrayMap<'T, 'TDictKey, 'TDictValue>(f: unit -> 'T[]) =
         match arrayStore with
         | NonNull value -> value
         | _ ->
-            Monitor.Enter(syncObj)
+            Monitor.Enter(this)
 
             try
                 match arrayStore with
@@ -176,14 +172,14 @@ type DelayInitArrayMap<'T, 'TDictKey, 'TDictValue>(f: unit -> 'T[]) =
                     func <- Unchecked.defaultof<_>
                     freshArray
             finally
-                Monitor.Exit(syncObj)
+                Monitor.Exit(this)
 
     member this.GetDictionary() =
         match dictStore with
         | NonNull value -> value
         | _ ->
             let array = this.GetArray()
-            Monitor.Enter(syncObj)
+            Monitor.Enter(this)
 
             try
                 match dictStore with
@@ -193,7 +189,7 @@ type DelayInitArrayMap<'T, 'TDictKey, 'TDictValue>(f: unit -> 'T[]) =
                     dictStore <- dict
                     dict
             finally
-                Monitor.Exit(syncObj)
+                Monitor.Exit(this)
 
     abstract CreateDictionary: 'T[] -> IDictionary<'TDictKey, 'TDictValue>