diff --git a/playground/ExternalServices/ExternalServices.AppHost/aspire-manifest.json b/playground/ExternalServices/ExternalServices.AppHost/aspire-manifest.json
index 27e3fc5a1b2..368edbe202f 100644
--- a/playground/ExternalServices/ExternalServices.AppHost/aspire-manifest.json
+++ b/playground/ExternalServices/ExternalServices.AppHost/aspire-manifest.json
@@ -41,4 +41,29 @@
     },
     "frontend": {
       "type": "project.v0",
-      "path": "../WebFrontEnd/WebFrontEnd.csproj"
\ No newline at end of file
+      "path": "../WebFrontEnd/WebFrontEnd.csproj",
+      "env": {
+        "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EXCEPTION_LOG_ATTRIBUTES": "true",
+        "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EVENT_LOG_ATTRIBUTES": "true",
+        "OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY": "in_memory",
+        "ASPNETCORE_FORWARDEDHEADERS_ENABLED": "true",
+        "HTTP_PORTS": "{frontend.bindings.http.targetPort}",
+        "services__nuget__https__0": "https://api.nuget.org/",
+        "EXTERNAL_SERVICE_URL": "{external-service-url.value}",
+        "services__gateway__http__0": "{gateway.bindings.http.url}"
+      },
+      "bindings": {
+        "http": {
+          "scheme": "http",
+          "protocol": "tcp",
+          "transport": "http"
+        },
+        "https": {
+          "scheme": "https",
+          "protocol": "tcp",
+          "transport": "http"
+        }
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/Aspire.Hosting/ResourceBuilderExtensions.cs b/src/Aspire.Hosting/ResourceBuilderExtensions.cs
index 364d0c793c9..13c148cc7e5 100644
--- a/src/Aspire.Hosting/ResourceBuilderExtensions.cs
+++ b/src/Aspire.Hosting/ResourceBuilderExtensions.cs
@@ -179,12 +179,14 @@ public static IResourceBuilder<T> WithEnvironment<T>(this IResourceBuilder<T> bu
         {
             builder.WithEnvironment(async context =>
             {
-                var url = await externalService.Resource.UrlParameter.GetValueAsync(context.CancellationToken).ConfigureAwait(false);
-
                 // In publish mode we can't validate the parameter value so we'll just use it without validating.
-                if (!context.ExecutionContext.IsPublishMode && !ExternalServiceResource.UrlIsValidForExternalService(url, out var _, out var message))
+                if (!context.ExecutionContext.IsPublishMode)
                 {
-                    throw new DistributedApplicationException($"The URL parameter '{externalService.Resource.UrlParameter.Name}' for the external service '{externalService.Resource.Name}' is invalid: {message}");
+                    var url = await externalService.Resource.UrlParameter.GetValueAsync(context.CancellationToken).ConfigureAwait(false);
+                    if (!ExternalServiceResource.UrlIsValidForExternalService(url, out var _, out var message))
+                    {
+                        throw new DistributedApplicationException($"The URL parameter '{externalService.Resource.UrlParameter.Name}' for the external service '{externalService.Resource.Name}' is invalid: {message}");
+                    }
                 }
 
                 context.EnvironmentVariables[name] = externalService.Resource.UrlParameter;
diff --git a/tests/Aspire.Hosting.Tests/ExternalServiceTests.cs b/tests/Aspire.Hosting.Tests/ExternalServiceTests.cs
index 9cdc3652d53..aae26da9132 100644
--- a/tests/Aspire.Hosting.Tests/ExternalServiceTests.cs
+++ b/tests/Aspire.Hosting.Tests/ExternalServiceTests.cs
@@ -443,6 +443,23 @@ public async Task ExternalServiceWithParameterHttpHealthCheckResolvesUrlAsync()
         Assert.Contains(healthCheckKey, result.Entries.Keys);
     }
 
+    [Fact]
+    public async Task ExternalServiceWithParameterPublishManifest()
+    {
+        using var builder = TestDistributedApplicationBuilder.Create(DistributedApplicationOperation.Publish);
+
+        var urlParam = builder.AddParameter("external-url");
+        var externalService = builder.AddExternalService("external", urlParam);
+
+        var project = builder.AddProject<TestProject>("project")
+                     .WithReference(externalService)
+                     .WithEnvironment("EXTERNAL_SERVICE", externalService);
+
+        var manifest = await ManifestUtils.GetManifest(project.Resource);
+
+        await Verify(manifest.ToString(), extension: "json");
+    }
+
     private sealed class TestProject : IProjectMetadata
     {
         public string ProjectPath => "testproject";
diff --git a/tests/Aspire.Hosting.Tests/Snapshots/ExternalServiceTests.ExternalServiceWithParameterPublishManifest.verified.json b/tests/Aspire.Hosting.Tests/Snapshots/ExternalServiceTests.ExternalServiceWithParameterPublishManifest.verified.json
new file mode 100644
index 00000000000..73910c77b68
--- /dev/null
+++ b/tests/Aspire.Hosting.Tests/Snapshots/ExternalServiceTests.ExternalServiceWithParameterPublishManifest.verified.json
@@ -0,0 +1,11 @@
+{
+  "type": "project.v0",
+  "path": "testproject",
+  "env": {
+    "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EXCEPTION_LOG_ATTRIBUTES": "true",
+    "OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EVENT_LOG_ATTRIBUTES": "true",
+    "OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY": "in_memory",
+    "services__external__default__0": "{external-url.value}",
+    "EXTERNAL_SERVICE": "{external-url.value}"
+  }
+}
\ No newline at end of file