diff --git a/source/WsFederationPlugin/ResponseHandling/MetadataResponseGenerator.cs b/source/WsFederationPlugin/ResponseHandling/MetadataResponseGenerator.cs
index added33..154d02b 100644
--- a/source/WsFederationPlugin/ResponseHandling/MetadataResponseGenerator.cs
+++ b/source/WsFederationPlugin/ResponseHandling/MetadataResponseGenerator.cs
@@ -16,11 +16,15 @@
 
 using IdentityModel.Constants;
 using IdentityServer3.Core.Configuration;
+using IdentityServer3.Core.Extensions;
+using IdentityServer3.Core.Services;
+using Microsoft.Owin;
 using System;
 using System.ComponentModel;
 using System.IdentityModel.Metadata;
 using System.IdentityModel.Protocols.WSTrust;
 using System.IdentityModel.Tokens;
+using System.Collections.Generic;
 
 #pragma warning disable 1591
 
@@ -30,10 +34,27 @@ namespace IdentityServer3.WsFederation.ResponseHandling
     public class MetadataResponseGenerator
     {
         private readonly IdentityServerOptions _options;
+        private readonly IDictionary<string, object> _environment;
 
-        public MetadataResponseGenerator(IdentityServerOptions options)
+        public MetadataResponseGenerator(IdentityServerOptions options, OwinEnvironmentService owin)
         {
             _options = options;
+            _environment = owin.Environment;
+        }
+
+        private string IssuerUri
+        {
+            get
+            {
+                var uri = _options.IssuerUri;
+                if (String.IsNullOrWhiteSpace(uri))
+                {
+                    uri = _environment.GetIdentityServerBaseUrl();
+                    if (uri.EndsWith("/")) uri = uri.Substring(0, uri.Length - 1);
+                }
+
+                return uri;
+            }
         }
 
         public EntityDescriptor Generate(string wsfedEndpoint)
@@ -41,7 +62,7 @@ public EntityDescriptor Generate(string wsfedEndpoint)
             var applicationDescriptor = GetApplicationDescriptor(wsfedEndpoint);
             var tokenServiceDescriptor = GetTokenServiceDescriptor(wsfedEndpoint);
 
-            var id = new EntityId(_options.IssuerUri);
+            var id = new EntityId(IssuerUri);
             var entity = new EntityDescriptor(id);
             entity.SigningCredentials = new X509SigningCredentials(_options.SigningCertificate);
             entity.RoleDescriptors.Add(applicationDescriptor);
diff --git a/source/WsFederationPlugin/ResponseHandling/SignInResponseGenerator.cs b/source/WsFederationPlugin/ResponseHandling/SignInResponseGenerator.cs
index 7eab079..9ddfd98 100644
--- a/source/WsFederationPlugin/ResponseHandling/SignInResponseGenerator.cs
+++ b/source/WsFederationPlugin/ResponseHandling/SignInResponseGenerator.cs
@@ -42,11 +42,28 @@ public class SignInResponseGenerator
         private readonly static ILog Logger = LogProvider.GetCurrentClassLogger();
         private readonly IdentityServerOptions _options;
         private readonly IUserService _users;
-        
-        public SignInResponseGenerator(IdentityServerOptions options, IUserService users)
+        private readonly IDictionary<string, object> _environment;
+
+        public SignInResponseGenerator(IdentityServerOptions options, IUserService users, OwinEnvironmentService owinEnvironment)
         {
             _options = options;
             _users = users;
+            _environment = owinEnvironment.Environment;
+        }
+
+        private string IssuerUri
+        {
+            get
+            {
+                var uri = _options.IssuerUri;
+                if (String.IsNullOrWhiteSpace(uri))
+                {
+                    uri = _environment.GetIdentityServerBaseUrl();
+                    if (uri.EndsWith("/")) uri = uri.Substring(0, uri.Length - 1);
+                }
+
+                return uri;
+            }
         }
 
         public async Task<SignInResponseMessage> GenerateResponseAsync(SignInValidationResult validationResult)
@@ -178,7 +195,7 @@ private SecurityToken CreateSecurityToken(SignInValidationResult validationResul
                 ReplyToAddress = validationResult.ReplyUrl,
                 SigningCredentials = new X509SigningCredentials(_options.SigningCertificate, validationResult.RelyingParty.SignatureAlgorithm, validationResult.RelyingParty.DigestAlgorithm),
                 Subject = outgoingSubject,
-                TokenIssuerName = _options.IssuerUri,
+                TokenIssuerName = IssuerUri,
                 TokenType = validationResult.RelyingParty.TokenType
             };