diff --git a/config/initializers/omniauth.rb b/config/initializers/omniauth.rb
index 97d52b9b5..197f98f07 100644
--- a/config/initializers/omniauth.rb
+++ b/config/initializers/omniauth.rb
@@ -31,12 +31,10 @@
   end
 
   SETUP_PROC = lambda do |env|
-    service = HostingEnvironment.current_service(Rack::Request.new(env))
+    request = Rack::Request.new(env)
+    service = HostingEnvironment.current_service(request)
 
-    dfe_sign_in_redirect_uri = URI.join(
-      HostingEnvironment.application_url(service),
-      "/auth/dfe/callback",
-    )
+    dfe_sign_in_redirect_uri = URI.join(request.base_url, "/auth/dfe/callback")
 
     env["omniauth.strategy"].options.client_options = {
       port: dfe_sign_in_issuer_uri&.port,
diff --git a/lib/hosting_environment.rb b/lib/hosting_environment.rb
index 3716d6ee9..42578dc39 100644
--- a/lib/hosting_environment.rb
+++ b/lib/hosting_environment.rb
@@ -14,11 +14,6 @@ module HostingEnvironment
     placements: ENV["PLACEMENTS_DFE_SIGN_IN_SECRET"],
   }.with_indifferent_access.freeze
 
-  SERVICE_HOST = {
-    claims: ENV["CLAIMS_HOST"],
-    placements: ENV["PLACEMENTS_HOST"],
-  }.with_indifferent_access.freeze
-
   def self.env
     @env ||= ActiveSupport::EnvironmentInquirer.new(ENV["HOSTING_ENV"].presence || "development")
   end
@@ -39,14 +34,6 @@ def self.dfe_sign_in_secret(current_service)
     DFE_SIGN_IN_CLIENT_SECRETS.fetch(current_service)
   end
 
-  def self.application_url(current_service)
-    if Rails.env.development?
-      "http://#{SERVICE_HOST.fetch(current_service)}:#{ENV.fetch("PORT", 3000)}"
-    else
-      "https://#{SERVICE_HOST.fetch(current_service)}"
-    end
-  end
-
   def self.current_service(request)
     case request.host
     when ENV["CLAIMS_HOST"], *ENV.fetch("CLAIMS_HOSTS", "").split(",")
diff --git a/spec/lib/hosting_environment_spec.rb b/spec/lib/hosting_environment_spec.rb
index c14dcda22..b8522c8a8 100644
--- a/spec/lib/hosting_environment_spec.rb
+++ b/spec/lib/hosting_environment_spec.rb
@@ -88,42 +88,6 @@
     end
   end
 
-  describe ".application_url" do
-    it "returns the application url for claims" do
-      current_service = "claims"
-      expect(described_class.application_url(current_service)).to eq(
-        "https://claims.localhost",
-      )
-    end
-
-    it "returns the application url for placements" do
-      current_service = "placements"
-      expect(described_class.application_url(current_service)).to eq(
-        "https://placements.localhost",
-      )
-    end
-
-    context "when env is development" do
-      it "returns the application url for claims with port" do
-        allow(Rails.env).to receive(:development?).and_return(true)
-        current_service = "claims"
-
-        expect(described_class.application_url(current_service)).to eq(
-          "http://claims.localhost:3000",
-        )
-      end
-
-      it "returns the application url for placements with port" do
-        allow(Rails.env).to receive(:development?).and_return(true)
-        current_service = "placements"
-
-        expect(described_class.application_url(current_service)).to eq(
-          "http://placements.localhost:3000",
-        )
-      end
-    end
-  end
-
   describe ".current_service" do
     it "returns the current service for claims" do
       request = instance_double("Rack::Request", host: ENV["CLAIMS_HOST"])