diff --git a/src/OpenIddict.Abstractions/Resources/OpenIddictResources.resx b/src/OpenIddict.Abstractions/Resources/OpenIddictResources.resx
index c4fbcd42..f80328ab 100644
--- a/src/OpenIddict.Abstractions/Resources/OpenIddictResources.resx
+++ b/src/OpenIddict.Abstractions/Resources/OpenIddictResources.resx
@@ -1776,6 +1776,10 @@ To register the OpenIddict core services, reference the 'OpenIddict.Core' packag
     <value>The token shouldn't be null or empty at this point.</value>
     <comment>{Locked}</comment>
   </data>
+  <data name="ID5011" xml:space="preserve">
+    <value>The OpenIddict Core services should be registered.</value>
+    <comment>{Locked}</comment>
+  </data>
   <data name="ID7000" xml:space="preserve">
     <value>An error occurred while validating the token '{Token}'.</value>
     <comment>{Locked}</comment>
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
index 8db9b064..e01c61c5 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.Authentication.cs
@@ -1080,13 +1080,15 @@ namespace OpenIddict.Server
 
             /// <summary>
             /// Contains the logic responsible of rejecting authorization requests that use unregistered scopes.
-            /// Note: this handler is not used when the degraded mode is enabled or when scope validation is disabled.
+            /// Note: this handler partially works with the degraded mode but is not used when scope validation is disabled.
             /// </summary>
             public class ValidateScopes : IOpenIddictServerHandler<ValidateAuthorizationRequestContext>
             {
-                private readonly IOpenIddictScopeManager _scopeManager;
+                private readonly IOpenIddictScopeManager? _scopeManager;
 
-                public ValidateScopes() => throw new InvalidOperationException(SR.GetResourceString(SR.ID1015));
+                public ValidateScopes()
+                {
+                }
 
                 public ValidateScopes(IOpenIddictScopeManager scopeManager)
                     => _scopeManager = scopeManager;
@@ -1097,7 +1099,6 @@ namespace OpenIddict.Server
                 public static OpenIddictServerHandlerDescriptor Descriptor { get; }
                     = OpenIddictServerHandlerDescriptor.CreateBuilder<ValidateAuthorizationRequestContext>()
                         .AddFilter<RequireScopeValidationEnabled>()
-                        .AddFilter<RequireDegradedModeDisabled>()
                         .UseScopedHandler<ValidateScopes>()
                         .SetOrder(ValidateClientRedirectUri.Descriptor.Order + 1_000)
                         .SetType(OpenIddictServerHandlerType.BuiltIn)
@@ -1115,8 +1116,13 @@ namespace OpenIddict.Server
                     var scopes = new HashSet<string>(context.Request.GetScopes(), StringComparer.Ordinal);
                     scopes.ExceptWith(context.Options.Scopes);
 
-                    if (scopes.Count != 0)
+                    // Note: the remaining scopes are only checked if the degraded mode was not enabled,
+                    // as this requires using the scope manager, which is never used with the degraded mode,
+                    // even if the service was registered and resolved from the dependency injection container.
+                    if (scopes.Count != 0 && !context.Options.EnableDegradedMode)
                     {
+                        Debug.Assert(_scopeManager != null, SR.GetResourceString(SR.ID5011));
+
                         await foreach (var scope in _scopeManager.FindByNamesAsync(scopes.ToImmutableArray()))
                         {
                             var name = await _scopeManager.GetNameAsync(scope);
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.Device.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.Device.cs
index b767d343..9904622c 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.Device.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.Device.cs
@@ -364,13 +364,15 @@ namespace OpenIddict.Server
 
             /// <summary>
             /// Contains the logic responsible of rejecting authorization requests that use unregistered scopes.
-            /// Note: this handler is not used when the degraded mode is enabled or when scope validation is disabled.
+            /// Note: this handler partially works with the degraded mode but is not used when scope validation is disabled.
             /// </summary>
             public class ValidateScopes : IOpenIddictServerHandler<ValidateDeviceRequestContext>
             {
-                private readonly IOpenIddictScopeManager _scopeManager;
+                private readonly IOpenIddictScopeManager? _scopeManager;
 
-                public ValidateScopes() => throw new InvalidOperationException(SR.GetResourceString(SR.ID1015));
+                public ValidateScopes()
+                {
+                }
 
                 public ValidateScopes(IOpenIddictScopeManager scopeManager)
                     => _scopeManager = scopeManager;
@@ -381,7 +383,6 @@ namespace OpenIddict.Server
                 public static OpenIddictServerHandlerDescriptor Descriptor { get; }
                     = OpenIddictServerHandlerDescriptor.CreateBuilder<ValidateDeviceRequestContext>()
                         .AddFilter<RequireScopeValidationEnabled>()
-                        .AddFilter<RequireDegradedModeDisabled>()
                         .UseScopedHandler<ValidateScopes>()
                         .SetOrder(ValidateClientIdParameter.Descriptor.Order + 1_000)
                         .SetType(OpenIddictServerHandlerType.BuiltIn)
@@ -399,8 +400,13 @@ namespace OpenIddict.Server
                     var scopes = new HashSet<string>(context.Request.GetScopes(), StringComparer.Ordinal);
                     scopes.ExceptWith(context.Options.Scopes);
 
-                    if (scopes.Count != 0)
+                    // Note: the remaining scopes are only checked if the degraded mode was not enabled,
+                    // as this requires using the scope manager, which is never used with the degraded mode,
+                    // even if the service was registered and resolved from the dependency injection container.
+                    if (scopes.Count != 0 && !context.Options.EnableDegradedMode)
                     {
+                        Debug.Assert(_scopeManager != null, SR.GetResourceString(SR.ID5011));
+
                         await foreach (var scope in _scopeManager.FindByNamesAsync(scopes.ToImmutableArray()))
                         {
                             var name = await _scopeManager.GetNameAsync(scope);
diff --git a/src/OpenIddict.Server/OpenIddictServerHandlers.Exchange.cs b/src/OpenIddict.Server/OpenIddictServerHandlers.Exchange.cs
index ebfea6eb..10777c2e 100644
--- a/src/OpenIddict.Server/OpenIddictServerHandlers.Exchange.cs
+++ b/src/OpenIddict.Server/OpenIddictServerHandlers.Exchange.cs
@@ -645,13 +645,15 @@ namespace OpenIddict.Server
 
             /// <summary>
             /// Contains the logic responsible of rejecting authorization requests that use unregistered scopes.
-            /// Note: this handler is not used when the degraded mode is enabled or when scope validation is disabled.
+            /// Note: this handler partially works with the degraded mode but is not used when scope validation is disabled.
             /// </summary>
             public class ValidateScopes : IOpenIddictServerHandler<ValidateTokenRequestContext>
             {
-                private readonly IOpenIddictScopeManager _scopeManager;
+                private readonly IOpenIddictScopeManager? _scopeManager;
 
-                public ValidateScopes() => throw new InvalidOperationException(SR.GetResourceString(SR.ID1015));
+                public ValidateScopes()
+                {
+                }
 
                 public ValidateScopes(IOpenIddictScopeManager scopeManager)
                     => _scopeManager = scopeManager;
@@ -662,7 +664,6 @@ namespace OpenIddict.Server
                 public static OpenIddictServerHandlerDescriptor Descriptor { get; }
                     = OpenIddictServerHandlerDescriptor.CreateBuilder<ValidateTokenRequestContext>()
                         .AddFilter<RequireScopeValidationEnabled>()
-                        .AddFilter<RequireDegradedModeDisabled>()
                         .UseScopedHandler<ValidateScopes>()
                         .SetOrder(ValidatePasswordParameters.Descriptor.Order + 1_000)
                         .SetType(OpenIddictServerHandlerType.BuiltIn)
@@ -680,8 +681,13 @@ namespace OpenIddict.Server
                     var scopes = new HashSet<string>(context.Request.GetScopes(), StringComparer.Ordinal);
                     scopes.ExceptWith(context.Options.Scopes);
 
-                    if (scopes.Count != 0)
+                    // Note: the remaining scopes are only checked if the degraded mode was not enabled,
+                    // as this requires using the scope manager, which is never used with the degraded mode,
+                    // even if the service was registered and resolved from the dependency injection container.
+                    if (scopes.Count != 0 && !context.Options.EnableDegradedMode)
                     {
+                        Debug.Assert(_scopeManager != null, SR.GetResourceString(SR.ID5011));
+
                         await foreach (var scope in _scopeManager.FindByNamesAsync(scopes.ToImmutableArray()))
                         {
                             var name = await _scopeManager.GetNameAsync(scope);
diff --git a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Authentication.cs b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Authentication.cs
index 7f655ee1..5b4d3c0b 100644
--- a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Authentication.cs
+++ b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Authentication.cs
@@ -615,38 +615,8 @@ namespace OpenIddict.Server.IntegrationTests
             // Arrange
             await using var server = await CreateServerAsync(options =>
             {
+                options.EnableDegradedMode();
                 options.RegisterScopes("registered_scope");
-                options.SetRevocationEndpointUris(Array.Empty<Uri>());
-                options.DisableTokenStorage();
-                options.DisableSlidingRefreshTokenExpiration();
-
-                options.Services.AddSingleton(CreateApplicationManager(mock =>
-                {
-                    var application = new OpenIddictApplication();
-
-                    mock.Setup(manager => manager.FindByClientIdAsync("Fabrikam", It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(application);
-
-                    mock.Setup(manager => manager.ValidateRedirectUriAsync(application, "http://www.fabrikam.com/path", It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(true);
-
-                    mock.Setup(manager => manager.HasClientTypeAsync(application, ClientTypes.Public, It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(true);
-                }));
-
-                options.Services.AddSingleton(CreateApplicationManager(mock =>
-                {
-                    var application = new OpenIddictApplication();
-
-                    mock.Setup(manager => manager.FindByClientIdAsync("Fabrikam", It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(application);
-
-                    mock.Setup(manager => manager.ValidateRedirectUriAsync(application, "http://www.fabrikam.com/path", It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(true);
-
-                    mock.Setup(manager => manager.HasClientTypeAsync(application, ClientTypes.Public, It.IsAny<CancellationToken>()))
-                        .ReturnsAsync(true);
-                }));
 
                 options.AddEventHandler<HandleAuthorizationRequestContext>(builder =>
                     builder.UseInlineHandler(context =>
diff --git a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Exchange.cs b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Exchange.cs
index 0d5821b8..d5905f8e 100644
--- a/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Exchange.cs
+++ b/test/OpenIddict.Server.IntegrationTests/OpenIddictServerIntegrationTests.Exchange.cs
@@ -886,6 +886,7 @@ namespace OpenIddict.Server.IntegrationTests
             await using var server = await CreateServerAsync(options =>
             {
                 options.EnableDegradedMode();
+                options.RegisterScopes(Scopes.Phone, Scopes.Profile);
 
                 options.AddEventHandler<ProcessAuthenticationContext>(builder =>
                 {
@@ -930,6 +931,7 @@ namespace OpenIddict.Server.IntegrationTests
             await using var server = await CreateServerAsync(options =>
             {
                 options.EnableDegradedMode();
+                options.RegisterScopes(Scopes.Phone, Scopes.Profile);
 
                 options.AddEventHandler<ProcessAuthenticationContext>(builder =>
                 {
@@ -974,6 +976,7 @@ namespace OpenIddict.Server.IntegrationTests
             await using var server = await CreateServerAsync(options =>
             {
                 options.EnableDegradedMode();
+                options.RegisterScopes(Scopes.Phone, Scopes.Profile);
 
                 options.AddEventHandler<ProcessAuthenticationContext>(builder =>
                 {
@@ -1016,6 +1019,7 @@ namespace OpenIddict.Server.IntegrationTests
             await using var server = await CreateServerAsync(options =>
             {
                 options.EnableDegradedMode();
+                options.RegisterScopes(Scopes.Phone, Scopes.Profile);
 
                 options.AddEventHandler<ProcessAuthenticationContext>(builder =>
                 {