diff --git a/src/coreclr/System.Private.CoreLib/src/System/Threading/Monitor.CoreCLR.cs b/src/coreclr/System.Private.CoreLib/src/System/Threading/Monitor.CoreCLR.cs
index 05a418e2f986a0..c271c2a3d55278 100644
--- a/src/coreclr/System.Private.CoreLib/src/System/Threading/Monitor.CoreCLR.cs
+++ b/src/coreclr/System.Private.CoreLib/src/System/Threading/Monitor.CoreCLR.cs
@@ -59,7 +59,7 @@ private enum LeaveHelperAction
             Yield = 2,
             Contention = 3,
             Error = 4,
-        };
+        }
 
         [MethodImpl(MethodImplOptions.InternalCall)]
         private static extern EnterHelperResult TryEnter_FastPath_WithTimeout(object obj, int timeout);
@@ -92,6 +92,8 @@ private static bool TryEnter_Slowpath(object obj)
         [MethodImpl(MethodImplOptions.NoInlining)]
         private static bool TryEnter_Slowpath(object obj, int timeout)
         {
+            ArgumentOutOfRangeException.ThrowIfLessThan(timeout, -1, null);
+
             if (TryEnter_Slowpath(ObjectHandleOnStack.Create(ref obj), timeout) != 0)
             {
                 return true;
@@ -170,13 +172,12 @@ internal static void ExitIfLockTaken(object obj, ref bool lockTaken)
             {
                 LeaveHelperAction exitBehavior = Exit_FastPath(obj);
 
-                if (exitBehavior == LeaveHelperAction.None)
+                if (exitBehavior != LeaveHelperAction.None)
                 {
-                    lockTaken = false;
+                    Exit_Slowpath(exitBehavior, obj);
                     return;
                 }
 
-                Exit_Slowpath(exitBehavior, obj);
                 lockTaken = false;
             }
         }
diff --git a/src/coreclr/classlibnative/bcltype/objectnative.cpp b/src/coreclr/classlibnative/bcltype/objectnative.cpp
index 791745075c9c7c..2a06cf22e737be 100644
--- a/src/coreclr/classlibnative/bcltype/objectnative.cpp
+++ b/src/coreclr/classlibnative/bcltype/objectnative.cpp
@@ -224,14 +224,7 @@ FCIMPL1(FC_BOOL_RET, ObjectNative::Monitor_TryEnter_FastPath, Object* obj)
 {
     FCALL_CONTRACT;
 
-    if (obj->TryEnterObjMonitorSpinHelper())
-    {
-        FC_RETURN_BOOL(TRUE);
-    }
-    else
-    {
-        FC_RETURN_BOOL(FALSE);
-    }
+    FC_RETURN_BOOL(obj->TryEnterObjMonitorSpinHelper());
 }
 FCIMPLEND
 
@@ -274,8 +267,7 @@ extern "C" INT32 QCALLTYPE Monitor_TryEnter_Slowpath(QCall::ObjectHandleOnStack
 
     GCX_COOP();
 
-    if (timeOut < -1)
-        COMPlusThrow(kArgumentOutOfRangeException);
+    _ASSERTE(timeOut >= -1); // This should be checked in managed code.
 
     result = objHandle.Get()->TryEnterObjMonitor(timeOut);