diff --git a/lib/saml_idp/request.rb b/lib/saml_idp/request.rb
index 5a3a3679..c6420c79 100644
--- a/lib/saml_idp/request.rb
+++ b/lib/saml_idp/request.rb
@@ -78,10 +78,10 @@ def response_url
     end
 
     def log(msg)
-      if config.logger.class <= ::Logger
-        config.logger.info msg
-      else
+      if config.logger.respond_to?(:call)
         config.logger.call msg
+      else
+        config.logger.info msg
       end
     end
 
@@ -198,4 +198,4 @@ def service_provider_finder
     end
     private :service_provider_finder
   end
-end
+end
\ No newline at end of file
diff --git a/spec/lib/saml_idp/request_spec.rb b/spec/lib/saml_idp/request_spec.rb
index a989a73c..339ea407 100644
--- a/spec/lib/saml_idp/request_spec.rb
+++ b/spec/lib/saml_idp/request_spec.rb
@@ -91,6 +91,23 @@ module SamlIdp
           end
         end
 
+        context 'a Logger-like logger is configured' do
+          let(:logger) do
+            Class.new {
+              def info(msg); end
+            }.new
+          end
+
+          before do
+            allow(logger).to receive(:info)
+          end
+
+          it 'logs an error message' do
+            expect(subject.valid?).to be false
+            expect(logger).to have_received(:info).with('Unable to find service provider for issuer ')
+          end
+        end
+
         context 'a logger lambda is configured' do
           let(:logger) { double }
 
@@ -138,4 +155,4 @@ module SamlIdp
       end
     end
   end
-end
+end
\ No newline at end of file