diff --git a/src/BuiltInTools/HotReloadAgent/HotReloadAgent.cs b/src/BuiltInTools/HotReloadAgent/HotReloadAgent.cs
index f64180144078..61af429cfd25 100644
--- a/src/BuiltInTools/HotReloadAgent/HotReloadAgent.cs
+++ b/src/BuiltInTools/HotReloadAgent/HotReloadAgent.cs
@@ -297,8 +297,12 @@ public void ApplyStaticAssetUpdate(RuntimeStaticAssetUpdate update)
     /// </summary>
     public static void ClearHotReloadEnvironmentVariables(Type startupHookType)
     {
-        Environment.SetEnvironmentVariable(AgentEnvironmentVariables.DotNetStartupHooks,
-            RemoveCurrentAssembly(startupHookType, Environment.GetEnvironmentVariable(AgentEnvironmentVariables.DotNetStartupHooks)!));
+        var startupHooks = Environment.GetEnvironmentVariable(AgentEnvironmentVariables.DotNetStartupHooks);
+        if (!string.IsNullOrEmpty(startupHooks))
+        {
+            Environment.SetEnvironmentVariable(AgentEnvironmentVariables.DotNetStartupHooks,
+                RemoveCurrentAssembly(startupHookType, startupHooks));
+        }
 
         Environment.SetEnvironmentVariable(AgentEnvironmentVariables.DotNetWatchHotReloadNamedPipeName, null);
         Environment.SetEnvironmentVariable(AgentEnvironmentVariables.HotReloadDeltaClientLogMessages, null);
@@ -307,10 +311,7 @@ public static void ClearHotReloadEnvironmentVariables(Type startupHookType)
     // internal for testing
     internal static string RemoveCurrentAssembly(Type startupHookType, string environment)
     {
-        if (environment is "")
-        {
-            return environment;
-        }
+        Debug.Assert(!string.IsNullOrEmpty(environment), $"{nameof(environment)} must be set");
 
         var comparison = Path.DirectorySeparatorChar == '\\' ? StringComparison.OrdinalIgnoreCase : StringComparison.Ordinal;
 
diff --git a/test/Microsoft.Extensions.DotNetDeltaApplier.Tests/HotReloadAgentTest.cs b/test/Microsoft.Extensions.DotNetDeltaApplier.Tests/HotReloadAgentTest.cs
index ce3644bd4e6a..7125d426fcdc 100644
--- a/test/Microsoft.Extensions.DotNetDeltaApplier.Tests/HotReloadAgentTest.cs
+++ b/test/Microsoft.Extensions.DotNetDeltaApplier.Tests/HotReloadAgentTest.cs
@@ -9,6 +9,24 @@ namespace Microsoft.DotNet.Watch.UnitTests
 {
     public class HotReloadAgentTest
     {
+        [Fact]
+        public void ClearHotReloadEnvironmentVariables_DoesNotThrow_WhenStartupHooksNotSet()
+        {
+            // Ensure DOTNET_STARTUP_HOOKS is not set
+            var original = Environment.GetEnvironmentVariable("DOTNET_STARTUP_HOOKS");
+            try
+            {
+                Environment.SetEnvironmentVariable("DOTNET_STARTUP_HOOKS", null);
+
+                // Should not throw NullReferenceException
+                HotReloadAgent.ClearHotReloadEnvironmentVariables(typeof(StartupHook));
+            }
+            finally
+            {
+                Environment.SetEnvironmentVariable("DOTNET_STARTUP_HOOKS", original);
+            }
+        }
+
         [Fact]
         public void ClearHotReloadEnvironmentVariables_ClearsStartupHook()
         {