diff --git a/src/NuGetMirror/FilterLogger.cs b/src/NuGetMirror/FilterLogger.cs
index 5a8f2aa..b43db67 100644
--- a/src/NuGetMirror/FilterLogger.cs
+++ b/src/NuGetMirror/FilterLogger.cs
@@ -7,23 +7,25 @@ namespace NuGetMirror
     public class FilterLogger : LoggerBase
     {
         public bool Enabled { get; set; } = true;
-
         public ILogger OutputLogger { get; }
 
-        public FilterLogger(ILogger output)
-            : this(output, LogLevel.Error)
+        public FilterLogger(ILogger output) : this(output, LogLevel.Error)
         {
         }
 
         public FilterLogger(ILogger output, LogLevel level)
         {
+            ArgumentNullException.ThrowIfNull(output);
+
             VerbosityLevel = level;
             OutputLogger = output;
         }
 
         public override void Log(ILogMessage message)
         {
-            if (Enabled && (int)message.Level >= (int)VerbosityLevel)
+            ArgumentNullException.ThrowIfNull(message);
+
+            if (Enabled && message.Level >= VerbosityLevel)
             {
                 OutputLogger.Log(message);
             }
@@ -31,12 +33,14 @@ public override void Log(ILogMessage message)
 
         public override Task LogAsync(ILogMessage message)
         {
-            if (Enabled && (int)message.Level >= (int)VerbosityLevel)
+            ArgumentNullException.ThrowIfNull(message);
+
+            if (Enabled && message.Level >= VerbosityLevel)
             {
                 return OutputLogger.LogAsync(message);
             }
 
-            return Task.FromResult(0);
+            return Task.CompletedTask;
         }
     }
 }