diff --git a/docs/_entities/conversation.md b/docs/_entities/conversation.md
index 41e2f36..4d099ca 100644
--- a/docs/_entities/conversation.md
+++ b/docs/_entities/conversation.md
@@ -6,14 +6,14 @@ This entity represents a private conversation between persons.
 
 ## Properties
 
-| Property       | Type (Length)                 | Description                                                                                                    |
-| -------------- | ----------------------------- | -------------------------------------------------------------------------------------------------------------- |
-| `author`       | [diaspora\* ID][diaspora-id]  | The diaspora\* ID of the author of the conversation.                                                           |
-| `guid`         | [GUID][guid]                  | The GUID of the conversation.                                                                                  |
-| `subject`      | [String][string] (255)        | The subject of the conversation.                                                    |
-| `created_at`   | [Timestamp][timestamp]        | The create timestamp of the conversation.                                                                      |
-| `participants` | [diaspora\* ID][diaspora-id]s | diaspora\* IDs of all participants of this conversation, including the `author`, seperated by `;`, at most 20. |
-| `message`      | [Message][message]            | The first Message in the conversation, needs to be the same `author`.                                          |
+| Property       | Type (Length)                 | Description                                                                                        |
+| -------------- | ----------------------------- | -------------------------------------------------------------------------------------------------- |
+| `author`       | [diaspora\* ID][diaspora-id]  | The diaspora\* ID of the author of the conversation.                                               |
+| `guid`         | [GUID][guid]                  | The GUID of the conversation.                                                                      |
+| `subject`      | [String][string] (255)        | The subject of the conversation.                                                                   |
+| `created_at`   | [Timestamp][timestamp]        | The create timestamp of the conversation.                                                          |
+| `participants` | [diaspora\* ID][diaspora-id]s | diaspora\* IDs of all participants of this conversation, including the `author`, seperated by `;`. |
+| `message`      | [Message][message]            | The first Message in the conversation, needs to be the same `author`.                              |
 
 ## Example
 
diff --git a/lib/diaspora_federation/validators.rb b/lib/diaspora_federation/validators.rb
index b5095ea..864ab8e 100644
--- a/lib/diaspora_federation/validators.rb
+++ b/lib/diaspora_federation/validators.rb
@@ -19,7 +19,7 @@ end
 require "diaspora_federation/validators/rules/birthday"
 require "diaspora_federation/validators/rules/boolean"
 require "diaspora_federation/validators/rules/diaspora_id"
-require "diaspora_federation/validators/rules/diaspora_id_count"
+require "diaspora_federation/validators/rules/diaspora_id_list"
 require "diaspora_federation/validators/rules/guid"
 require "diaspora_federation/validators/rules/not_nil"
 require "diaspora_federation/validators/rules/public_key"
diff --git a/lib/diaspora_federation/validators/conversation_validator.rb b/lib/diaspora_federation/validators/conversation_validator.rb
index 43e68cb..d3d63a9 100644
--- a/lib/diaspora_federation/validators/conversation_validator.rb
+++ b/lib/diaspora_federation/validators/conversation_validator.rb
@@ -9,7 +9,7 @@ module DiasporaFederation
 
       rule :subject, [:not_empty, length: {maximum: 255}]
 
-      rule :participants, diaspora_id_count: {maximum: 20}
+      rule :participants, diaspora_id_list: {minimum: 2}
       rule :messages, :not_nil
     end
   end
diff --git a/lib/diaspora_federation/validators/rules/diaspora_id_count.rb b/lib/diaspora_federation/validators/rules/diaspora_id_count.rb
deleted file mode 100644
index 1709b87..0000000
--- a/lib/diaspora_federation/validators/rules/diaspora_id_count.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-module Validation
-  module Rule
-    # Rule for validating the number of diaspora* IDs in a string.
-    # The evaluated string is split at ";" and the result will be counted.
-    class DiasporaIdCount
-      # This rule must have a +maximum+ param.
-      # @return [Hash] params
-      attr_reader :params
-
-      # Creates a new rule for a maximum diaspora* ID count validation
-      # @param [Hash] params
-      # @option params [Integer] :maximum maximum allowed id count
-      def initialize(params)
-        unless params.include?(:maximum) && params[:maximum].is_a?(Integer)
-          raise ArgumentError, "A number has to be specified for :maximum"
-        end
-
-        @params = params
-      end
-
-      # The error key for this rule
-      # @return [Symbol] error key
-      def error_key
-        :diaspora_id_count
-      end
-
-      def valid_value?(value)
-        ids = value.split(";")
-        return false unless ids.count <= params[:maximum]
-        ids.each do |id|
-          return false if DiasporaId::DIASPORA_ID.match(id).nil?
-        end
-        true
-      end
-    end
-  end
-end
diff --git a/lib/diaspora_federation/validators/rules/diaspora_id_list.rb b/lib/diaspora_federation/validators/rules/diaspora_id_list.rb
new file mode 100644
index 0000000..85e1937
--- /dev/null
+++ b/lib/diaspora_federation/validators/rules/diaspora_id_list.rb
@@ -0,0 +1,41 @@
+module Validation
+  module Rule
+    # Rule for validating the number of diaspora* IDs in a string.
+    # The evaluated string is split at ";".
+    class DiasporaIdList
+      # This rule can have a +minimum+ or +maximum+ param.
+      # @return [Hash] params
+      attr_reader :params
+
+      # Creates a new rule for a diaspora* ID list validation
+      # @param [Hash] params
+      # @option params [Integer] :minimum minimum allowed id count
+      # @option params [Integer] :maximum maximum allowed id count
+      def initialize(params={})
+        %i[minimum maximum].each do |param|
+          if params.include?(param) && !params[param].is_a?(Integer)
+            raise ArgumentError, "The :#{param} needs to be an Integer"
+          end
+        end
+
+        @params = params
+      end
+
+      # The error key for this rule
+      # @return [Symbol] error key
+      def error_key
+        :diaspora_id_list
+      end
+
+      def valid_value?(value)
+        ids = value.split(";")
+        return false if params.include?(:maximum) && ids.count > params[:maximum]
+        return false if params.include?(:minimum) && ids.count < params[:minimum]
+        ids.each do |id|
+          return false if DiasporaId::DIASPORA_ID.match(id).nil?
+        end
+        true
+      end
+    end
+  end
+end
diff --git a/spec/lib/diaspora_federation/validators/conversation_validator_spec.rb b/spec/lib/diaspora_federation/validators/conversation_validator_spec.rb
index 49670ff..d5f93a9 100644
--- a/spec/lib/diaspora_federation/validators/conversation_validator_spec.rb
+++ b/spec/lib/diaspora_federation/validators/conversation_validator_spec.rb
@@ -29,11 +29,15 @@ module DiasporaFederation
     end
 
     describe "#participant_ids" do
-      # must not contain more than 20 participant handles
       it_behaves_like "a property with a value validation/restriction" do
         let(:property) { :participants }
-        let(:wrong_values) { [Array.new(21) { Fabricate.sequence(:diaspora_id) }.join(";")] }
-        let(:correct_values) { [Array.new(20) { Fabricate.sequence(:diaspora_id) }.join(";")] }
+        let(:wrong_values) { ["", "foo;bar", Fabricate.sequence(:diaspora_id)] }
+        let(:correct_values) {
+          [
+            Array.new(2) { Fabricate.sequence(:diaspora_id) }.join(";"),
+            Array.new(21) { Fabricate.sequence(:diaspora_id) }.join(";")
+          ]
+        }
       end
     end
   end
diff --git a/spec/lib/diaspora_federation/validators/rules/diaspora_id_count_spec.rb b/spec/lib/diaspora_federation/validators/rules/diaspora_id_count_spec.rb
deleted file mode 100644
index 5d927b4..0000000
--- a/spec/lib/diaspora_federation/validators/rules/diaspora_id_count_spec.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-describe Validation::Rule::DiasporaIdCount do
-  let(:id_str) { Array.new(3) { Fabricate.sequence(:diaspora_id) }.join(";") }
-
-  it "requires a parameter" do
-    validator = Validation::Validator.new({})
-    expect {
-      validator.rule(:ids, :diaspora_id_count)
-    }.to raise_error ArgumentError
-  end
-
-  it "requires a integer as parameter" do
-    validator = Validation::Validator.new({})
-    [nil, "", 5.5].each do |val|
-      expect {
-        validator.rule(:ids, diaspora_id_count: {maximum: val})
-      }.to raise_error ArgumentError, "A number has to be specified for :maximum"
-    end
-  end
-
-  it "has an error key" do
-    expect(described_class.new(maximum: 5).error_key).to eq(:diaspora_id_count)
-  end
-
-  context "validation" do
-    it "validates less ids" do
-      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
-      validator.rule(:ids, diaspora_id_count: {maximum: 5})
-
-      expect(validator).to be_valid
-      expect(validator.errors).to be_empty
-    end
-
-    it "fails for less but non ids" do
-      bad_str = "user@example.com;i am a weird diaspora* ID @@@ ### 12345;shouldnt be reached by a rule"
-      validator = Validation::Validator.new(OpenStruct.new(ids: bad_str))
-      validator.rule(:ids, diaspora_id_count: {maximum: 5})
-
-      expect(validator).not_to be_valid
-      expect(validator.errors).to include(:ids)
-    end
-
-    it "validates exactly as many ids" do
-      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
-      validator.rule(:ids, diaspora_id_count: {maximum: 3})
-
-      expect(validator).to be_valid
-      expect(validator.errors).to be_empty
-    end
-
-    it "fails for too many ids" do
-      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
-      validator.rule(:ids, diaspora_id_count: {maximum: 1})
-
-      expect(validator).not_to be_valid
-      expect(validator.errors).to include(:ids)
-    end
-  end
-end
diff --git a/spec/lib/diaspora_federation/validators/rules/diaspora_id_list_spec.rb b/spec/lib/diaspora_federation/validators/rules/diaspora_id_list_spec.rb
new file mode 100644
index 0000000..d6ad026
--- /dev/null
+++ b/spec/lib/diaspora_federation/validators/rules/diaspora_id_list_spec.rb
@@ -0,0 +1,90 @@
+describe Validation::Rule::DiasporaIdList do
+  let(:id_str) { Array.new(3) { Fabricate.sequence(:diaspora_id) }.join(";") }
+
+  it "does not require a parameter" do
+    validator = Validation::Validator.new({})
+    expect {
+      validator.rule(:ids, :diaspora_id_list)
+    }.not_to raise_error
+  end
+
+  it "allows a :maximum parameter" do
+    validator = Validation::Validator.new({})
+    expect {
+      validator.rule(:ids, diaspora_id_list: {maximum: 20})
+    }.not_to raise_error
+  end
+
+  it "requires a integer as :maximum" do
+    validator = Validation::Validator.new({})
+    [nil, "", 5.5].each do |val|
+      expect {
+        validator.rule(:ids, diaspora_id_list: {maximum: val})
+      }.to raise_error ArgumentError, "The :maximum needs to be an Integer"
+    end
+  end
+
+  it "requires a integer as :minimum" do
+    validator = Validation::Validator.new({})
+    [nil, "", 5.5].each do |val|
+      expect {
+        validator.rule(:ids, diaspora_id_list: {minimum: val})
+      }.to raise_error ArgumentError, "The :minimum needs to be an Integer"
+    end
+  end
+
+  it "has an error key" do
+    expect(described_class.new(maximum: 5).error_key).to eq(:diaspora_id_list)
+  end
+
+  context "validation" do
+    it "validates less ids" do
+      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
+      validator.rule(:ids, diaspora_id_list: {maximum: 5})
+
+      expect(validator).to be_valid
+      expect(validator.errors).to be_empty
+    end
+
+    it "fails for less but non ids" do
+      bad_str = "user@example.com;i am a weird diaspora* ID @@@ ### 12345;shouldnt be reached by a rule"
+      validator = Validation::Validator.new(OpenStruct.new(ids: bad_str))
+      validator.rule(:ids, diaspora_id_list: {maximum: 5})
+
+      expect(validator).not_to be_valid
+      expect(validator.errors).to include(:ids)
+    end
+
+    it "validates exactly as many ids" do
+      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
+      validator.rule(:ids, diaspora_id_list: {minimum: 3, maximum: 3})
+
+      expect(validator).to be_valid
+      expect(validator.errors).to be_empty
+    end
+
+    it "validates without params" do
+      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
+      validator.rule(:ids, :diaspora_id_list)
+
+      expect(validator).to be_valid
+      expect(validator.errors).to be_empty
+    end
+
+    it "fails for too many ids" do
+      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
+      validator.rule(:ids, diaspora_id_list: {maximum: 2})
+
+      expect(validator).not_to be_valid
+      expect(validator.errors).to include(:ids)
+    end
+
+    it "fails for too less ids" do
+      validator = Validation::Validator.new(OpenStruct.new(ids: id_str))
+      validator.rule(:ids, diaspora_id_list: {minimum: 4})
+
+      expect(validator).not_to be_valid
+      expect(validator.errors).to include(:ids)
+    end
+  end
+end