diff --git a/src/Serilog/Configuration/LoggerSettingsConfiguration.cs b/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
index afd1499d3..cfde0fa1e 100644
--- a/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
+++ b/src/Serilog/Configuration/LoggerSettingsConfiguration.cs
@@ -14,6 +14,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
 using Serilog.Settings.KeyValuePairs;
 
 namespace Serilog.Configuration
@@ -52,7 +54,9 @@ public LoggerConfiguration Settings(ILoggerSettings settings)
         public LoggerConfiguration KeyValuePairs(IEnumerable<KeyValuePair<string, string>> settings)
         {
             if (settings == null) throw new ArgumentNullException(nameof(settings));
-            return Settings(new KeyValuePairSettings(settings));
+
+            var settingsDictionary = new ReadOnlyDictionary<string, string>(settings.ToDictionary(x => x.Key, x => x.Value));
+            return Settings(new KeyValuePairSettings(settingsDictionary));
         }
     }
 }
diff --git a/src/Serilog/Settings/KeyValuePairs/KeyValuePairSettings.cs b/src/Serilog/Settings/KeyValuePairs/KeyValuePairSettings.cs
index 69c619efd..51bbcb1d1 100644
--- a/src/Serilog/Settings/KeyValuePairs/KeyValuePairSettings.cs
+++ b/src/Serilog/Settings/KeyValuePairs/KeyValuePairSettings.cs
@@ -73,21 +73,18 @@ class KeyValuePairSettings : ILoggerSettings
             [typeof(LoggerFilterConfiguration)] = lc => lc.Filter
         };
 
-        readonly Dictionary<string, string> _settings;
+        readonly IReadOnlyDictionary<string, string> _settings;
 
-        public KeyValuePairSettings(IEnumerable<KeyValuePair<string, string>> settings)
+        public KeyValuePairSettings(IReadOnlyDictionary<string, string> settings)
         {
-            if (settings == null) throw new ArgumentNullException(nameof(settings));
-            _settings = settings.ToDictionary(s => s.Key, s => s.Value);
+            _settings = settings ?? throw new ArgumentNullException(nameof(settings));
         }
 
         public void Configure(LoggerConfiguration loggerConfiguration)
         {
             if (loggerConfiguration == null) throw new ArgumentNullException(nameof(loggerConfiguration));
-
-            var directives = _settings.Keys
-                .Where(k => _supportedDirectives.Any(k.StartsWith))
-                .ToDictionary(k => k, k => _settings[k]);
+            
+            var directives = ExtractDirectives(_settings);
 
             var declaredLevelSwitches = ParseNamedLevelSwitchDeclarationDirectives(directives);
 
@@ -164,12 +161,21 @@ where matchCallables.IsMatch(wt.Key)
             }
         }
 
+        internal static IReadOnlyDictionary<string, string> ExtractDirectives(IReadOnlyDictionary<string, string> settings)
+        {
+            var directives = settings
+                .Where(kvp => _supportedDirectives.Any(kvp.Key.StartsWith))
+                .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
+
+            return new ReadOnlyDictionary<string, string>(directives);
+        }
+
         internal static bool IsValidSwitchName(string input)
         {
             return Regex.IsMatch(input, LevelSwitchNameRegex);
         }
 
-        static IReadOnlyDictionary<string, LoggingLevelSwitch> ParseNamedLevelSwitchDeclarationDirectives(Dictionary<string, string> directives)
+        static IReadOnlyDictionary<string, LoggingLevelSwitch> ParseNamedLevelSwitchDeclarationDirectives(IReadOnlyDictionary<string, string> directives)
         {
             var matchLevelSwitchDeclarations = new Regex(LevelSwitchDeclarationDirectiveRegex);
 
@@ -255,7 +261,7 @@ internal static MethodInfo SelectConfigurationMethod(IEnumerable<MethodInfo> can
                 .FirstOrDefault();
         }
 
-        internal static IEnumerable<Assembly> LoadConfigurationAssemblies(Dictionary<string, string> directives)
+        internal static IEnumerable<Assembly> LoadConfigurationAssemblies(IReadOnlyDictionary<string, string> directives)
         {
             var configurationAssemblies = new List<Assembly> { typeof(ILogger).GetTypeInfo().Assembly };
 
diff --git a/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs b/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
index 9b7e7f9fd..405a13a29 100644
--- a/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
+++ b/test/Serilog.Tests/Settings/KeyValuePairSettingsTests.cs
@@ -15,6 +15,35 @@ namespace Serilog.Tests.Settings
 {
     public class KeyValuePairSettingsTests
     {
+        [Fact]
+        public void DuplicateKeysCauseArgumentException()
+        {
+            Action action = () => new LoggerConfiguration()
+                .ReadFrom.KeyValuePairs(new List<KeyValuePair<string, string>>
+                {
+                    new KeyValuePair<string, string>("setting", "Value"),
+                    new KeyValuePair<string, string>("setting", "SameSettingOtherValue"),
+                });
+
+            var ex = Assert.ThrowsAny<ArgumentException>(action);
+            Assert.NotNull(ex);
+            Assert.Contains("An item with the same key has already been added.", ex.Message);
+        }
+
+        [Fact]
+        public void IrrelevantKeysAreIgnored()
+        {
+            var irrelevantSettings = new Dictionary<string, string>()
+            {
+                ["whatever:foo:bar"] = "willBeIgnored",
+                ["irrelevant"] = "willBeIgnored",
+            };
+
+            var directives = KeyValuePairSettings.ExtractDirectives(irrelevantSettings);
+
+            Assert.False(directives.Any());
+        }
+
         [Fact]
         public void FindsConfigurationAssemblies()
         {
@@ -181,7 +210,7 @@ public void LoggingLevelSwitchWithInvalidNameThrowsFormatException()
                 ["level-switch:switchNameNotStartingWithDollar"] = "Warning",
             };
 
-            var ex = Assert.Throws<FormatException>(() =>  new LoggerConfiguration()
+            var ex = Assert.Throws<FormatException>(() => new LoggerConfiguration()
                 .ReadFrom.KeyValuePairs(settings));
 
             Assert.Contains("\"switchNameNotStartingWithDollar\"", ex.Message);
@@ -301,7 +330,7 @@ public void LoggingLevelSwitchCanBeUsedForMinimumLevelOverrides()
                 .CreateLogger();
 
             var systemLogger = log.ForContext(Constants.SourceContextPropertyName, "System.Bar");
-            
+
             log.Write(Some.InformationEvent());
             Assert.False(evt is null, "Minimul level is Debug. It should log Information messages");