diff --git a/lib/diaspora_federation/entity.rb b/lib/diaspora_federation/entity.rb
index 944333a..ba294df 100644
--- a/lib/diaspora_federation/entity.rb
+++ b/lib/diaspora_federation/entity.rb
@@ -83,12 +83,11 @@ module DiasporaFederation
       entity_xml
     end
 
-    # some of this is from Rails "Inflector.demodulize" and "Inflector.undersore"
+    # Makes an underscored, lowercase form of the class name
+    # @return [String] entity name
     def self.entity_name
       name.rpartition("::").last.tap do |word|
-        word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2')
-        word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
-        word.tr!("-", "_")
+        word.gsub!(/(.)([A-Z])/, '\1_\2')
         word.downcase!
       end
     end
diff --git a/lib/diaspora_federation/salmon/xml_payload.rb b/lib/diaspora_federation/salmon/xml_payload.rb
index 25d70bb..664ac73 100644
--- a/lib/diaspora_federation/salmon/xml_payload.rb
+++ b/lib/diaspora_federation/salmon/xml_payload.rb
@@ -47,8 +47,8 @@ module DiasporaFederation
         raise InvalidStructure unless wrap_valid?(xml)
 
         data = xml.at_xpath("post/*[1]")
-        klass_name = entity_class(data.name)
-        raise UnknownEntity unless Entities.const_defined?(klass_name)
+        klass_name = entity_class_name(data.name)
+        raise UnknownEntity, "'#{klass_name}' not found" unless Entities.const_defined?(klass_name)
 
         klass = Entities.const_get(klass_name)
         populate_entity(klass, data)
@@ -66,16 +66,16 @@ module DiasporaFederation
       # Transform the given String from the lowercase underscored version to a
       # camelized variant, used later for getting the Class constant.
       #
-      # @note some of this is from Rails "Inflector.camelize"
-      #
       # @param [String] term "snake_case" class name
       # @return [String] "CamelCase" class name
-      def self.entity_class(term)
-        string = term.to_s
-        string = string.sub(/^[a-z\d]*/) { $&.capitalize }
-        string.gsub(%r{(?:_|(\/))([a-z\d]*)}i) { Regexp.last_match[2].capitalize }.gsub("/", "::")
+      def self.entity_class_name(term)
+        term.to_s.tap do |string|
+          raise InvalidEntityName, "'#{string}' is invalid" unless string =~ /^[a-z]*(_[a-z]*)*$/
+          string.sub!(/^[a-z]/, &:upcase)
+          string.gsub!(/_([a-z])/) { Regexp.last_match[1].upcase }
+        end
       end
-      private_class_method :entity_class
+      private_class_method :entity_class_name
 
       # Construct a new instance of the given Entity and populate the properties
       # with the attributes found in the XML.
@@ -114,6 +114,10 @@ module DiasporaFederation
       class InvalidStructure < RuntimeError
       end
 
+      # Raised, if the entity name in the XML is invalid
+      class InvalidEntityName < RuntimeError
+      end
+
       # Raised, if the entity contained within the XML cannot be mapped to a
       # defined {Entity} subclass.
       class UnknownEntity < RuntimeError
diff --git a/spec/entities.rb b/spec/entities.rb
index 2ecb901..4b487bd 100644
--- a/spec/entities.rb
+++ b/spec/entities.rb
@@ -25,6 +25,10 @@ module DiasporaFederation
       property :test
       property :qwer, xml_name: :asdf
     end
+
+    class Entity < DiasporaFederation::Entity
+      property :test
+    end
   end
 
   module Validators
diff --git a/spec/lib/diaspora_federation/entity_spec.rb b/spec/lib/diaspora_federation/entity_spec.rb
index 085bfb1..8bbd0b1 100644
--- a/spec/lib/diaspora_federation/entity_spec.rb
+++ b/spec/lib/diaspora_federation/entity_spec.rb
@@ -99,6 +99,10 @@ module DiasporaFederation
         expect(Entities::TestNestedEntity.entity_name).to eq("test_nested_entity")
         expect(Entities::OtherEntity.entity_name).to eq("other_entity")
       end
+
+      it "works with a single word" do
+        expect(Entities::Entity.entity_name).to eq("entity")
+      end
     end
 
     context "nested entities" do
diff --git a/spec/lib/diaspora_federation/salmon/xml_payload_spec.rb b/spec/lib/diaspora_federation/salmon/xml_payload_spec.rb
index 89094b1..b555220 100644
--- a/spec/lib/diaspora_federation/salmon/xml_payload_spec.rb
+++ b/spec/lib/diaspora_federation/salmon/xml_payload_spec.rb
@@ -67,6 +67,21 @@ XML
 
         it "raises an error when the xml is wrong" do
           xml = <<-XML
+<XML>
+  <post>
+    <unknown_entity>
+      <test>asdf</test>
+    </test_entity>
+  </post>
+</XML>
+XML
+          expect {
+            Salmon::XmlPayload.unpack(Nokogiri::XML::Document.parse(xml).root)
+          }.to raise_error Salmon::XmlPayload::UnknownEntity, "'UnknownEntity' not found"
+        end
+
+        it "raises an error when the entity is not found" do
+          xml = <<-XML
 <root>
   <weird/>
 </root>
@@ -108,6 +123,34 @@ XML
           expect(entity.asdf).to eq("QWERT")
         end
       end
+
+      context ".entity_class_name" do
+        it "should parse a single word" do
+          expect(Salmon::XmlPayload.send(:entity_class_name, "entity")).to eq("Entity")
+        end
+
+        it "should parse with underscore" do
+          expect(Salmon::XmlPayload.send(:entity_class_name, "test_entity")).to eq("TestEntity")
+        end
+
+        it "raises an error when the entity name contains special characters" do
+          expect {
+            Salmon::XmlPayload.send(:entity_class_name, "te.st-enti/ty")
+          }.to raise_error Salmon::XmlPayload::InvalidEntityName, "'te.st-enti/ty' is invalid"
+        end
+
+        it "raises an error when the entity name contains upper case letters" do
+          expect {
+            Salmon::XmlPayload.send(:entity_class_name, "TestEntity")
+          }.to raise_error Salmon::XmlPayload::InvalidEntityName, "'TestEntity' is invalid"
+        end
+
+        it "raises an error when the entity name contains numbers" do
+          expect {
+            Salmon::XmlPayload.send(:entity_class_name, "te5t_ent1ty_w1th_number5")
+          }.to raise_error Salmon::XmlPayload::InvalidEntityName, "'te5t_ent1ty_w1th_number5' is invalid"
+        end
+      end
     end
   end
 end