diff --git a/.gitignore b/.gitignore
index 9b2dc3edec9a83224c443c3d7e430dccb3450af1..3627b96f5329515f04d9e71e3ed73d6a45a0ed00 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,4 +16,5 @@ server.rb
 *.sw?
 /tmp/
 /_yardoc/
-.idea/
\ No newline at end of file
+.idea/
+
diff --git a/Gemfile b/Gemfile
index b4e2a20bb6069d33479542fc863e7e36810e0f01..9c886f687c742260ee1a06b1f7a704a6d4fe2d2e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,7 @@
 source "https://rubygems.org"
 
 gemspec
+
+group :development do
+  gem 'minitest', '~> 5.8', '>= 5.8.4'
+end
diff --git a/lib/ipaddress/ipv4.rb b/lib/ipaddress/ipv4.rb
index 7d8e0d377e9a08ec973bd478b3d6ee56dce96d91..a123e7116931b0e8d6b4dfbc5461c681c02a111b 100644
--- a/lib/ipaddress/ipv4.rb
+++ b/lib/ipaddress/ipv4.rb
@@ -634,20 +634,6 @@ module IPAddress;
       [self.class.new("224.0.0.0/4")].any? {|i| i.include? self}
     end
 
-    #
-    # Checks if an IPv4 address objects belongs
-    # to a multicast network RFC3171
-    #
-    # Example:
-    #
-    #   ip = IPAddress "224.0.0.0/4"
-    #   ip.multicast?
-    #     #=> true
-    #    
-    def multicast?
-      [self.class.new("224.0.0.0/4")].any? {|i| i.include? self}
-    end
-
     #
     # Checks if an IPv4 address objects belongs
     # to a loopback network RFC1122