diff --git a/ext/date/date.gemspec b/ext/date/date.gemspec
index f5649f8daa..a5accd29e6 100644
--- a/ext/date/date.gemspec
+++ b/ext/date/date.gemspec
@@ -17,5 +17,5 @@ Gem::Specification.new do |s|
   s.authors = ["Tadayoshi Funaba"]
   s.email = [nil]
   s.homepage = "https://github.com/ruby/date"
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 end
diff --git a/ext/dbm/dbm.gemspec b/ext/dbm/dbm.gemspec
index 02d4990ecb..0ff036f712 100644
--- a/ext/dbm/dbm.gemspec
+++ b/ext/dbm/dbm.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |s|
   s.authors = ["Yukihiro Matsumoto"]
   s.email = ["matz@ruby-lang.org"]
   s.homepage = "https://github.com/ruby/dbm"
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 
   s.add_development_dependency "rake-compiler"
   s.add_development_dependency "test-unit"
diff --git a/ext/etc/etc.gemspec b/ext/etc/etc.gemspec
index 1b39a6d59a..7d687e3b99 100644
--- a/ext/etc/etc.gemspec
+++ b/ext/etc/etc.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Provides access to information typically stored in UNIX /etc directory.}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/etc"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = %w[
     LICENSE.txt
diff --git a/ext/fcntl/fcntl.gemspec b/ext/fcntl/fcntl.gemspec
index c27a03d47a..645c507a4d 100644
--- a/ext/fcntl/fcntl.gemspec
+++ b/ext/fcntl/fcntl.gemspec
@@ -10,7 +10,7 @@ Gem::Specification.new do |spec|
   spec.summary       = "Loads constants defined in the OS fcntl.h C header file"
   spec.description   = "Loads constants defined in the OS fcntl.h C header file"
   spec.homepage      = "https://github.com/ruby/fcntl"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = ["ext/fcntl/extconf.rb", "ext/fcntl/fcntl.c"]
   spec.bindir        = "exe"
diff --git a/ext/fiddle/fiddle.gemspec b/ext/fiddle/fiddle.gemspec
index da57ea7dc7..a92955ccec 100644
--- a/ext/fiddle/fiddle.gemspec
+++ b/ext/fiddle/fiddle.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{A libffi wrapper for Ruby.}
   spec.description   = %q{A libffi wrapper for Ruby.}
   spec.homepage      = "https://github.com/ruby/fiddle"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [
     "LICENSE.txt",
diff --git a/ext/gdbm/gdbm.gemspec b/ext/gdbm/gdbm.gemspec
index da074b0180..3ecb3121fe 100644
--- a/ext/gdbm/gdbm.gemspec
+++ b/ext/gdbm/gdbm.gemspec
@@ -10,7 +10,7 @@ Gem::Specification.new do |spec|
   spec.summary       = "Ruby extension for GNU dbm."
   spec.description   = "Ruby extension for GNU dbm."
   spec.homepage      = "https://github.com/ruby/gdbm"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = ["ext/gdbm/extconf.rb", "ext/gdbm/gdbm.c"]
   spec.bindir        = "exe"
diff --git a/ext/io/console/io-console.gemspec b/ext/io/console/io-console.gemspec
index 297c994de9..743e5e965d 100644
--- a/ext/io/console/io-console.gemspec
+++ b/ext/io/console/io-console.gemspec
@@ -21,5 +21,5 @@ Gem::Specification.new do |s|
     lib/io/console/size.rb
   ]
   s.extensions = %w[ext/io/console/extconf.rb]
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 end
diff --git a/ext/readline/readline-ext.gemspec b/ext/readline/readline-ext.gemspec
index b85e07dd93..66db14d14a 100644
--- a/ext/readline/readline-ext.gemspec
+++ b/ext/readline/readline-ext.gemspec
@@ -7,7 +7,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Provides an interface for GNU Readline and Edit Line (libedit).}
   spec.description   = %q{Provides an interface for GNU Readline and Edit Line (libedit).}
   spec.homepage      = "https://github.com/ruby/readline-ext"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
   spec.extensions    = %w[ext/readline/extconf.rb]
 
   spec.metadata["homepage_uri"] = spec.homepage
diff --git a/ext/stringio/stringio.gemspec b/ext/stringio/stringio.gemspec
index 4849481786..c765242f35 100644
--- a/ext/stringio/stringio.gemspec
+++ b/ext/stringio/stringio.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |s|
   s.extensions = ["ext/stringio/extconf.rb"]
   s.files = ["README.md", "ext/stringio/extconf.rb", "ext/stringio/stringio.c"]
   s.homepage = "https://github.com/ruby/stringio"
-  s.licenses = ["BSD-2-Clause"]
+  s.licenses = ["Ruby", "BSD-2-Clause"]
   s.required_ruby_version = ">= 2.5"
   s.summary = "Pseudo IO on String"
 
diff --git a/ext/strscan/strscan.gemspec b/ext/strscan/strscan.gemspec
index 4759c6c860..1228e80804 100644
--- a/ext/strscan/strscan.gemspec
+++ b/ext/strscan/strscan.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |s|
   s.authors = ["Minero Aoki", "Sutou Kouhei"]
   s.email = [nil, "kou@cozmixng.org"]
   s.homepage = "https://github.com/ruby/strscan"
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 
   s.add_development_dependency "rake-compiler"
   s.add_development_dependency "benchmark-driver"
diff --git a/ext/zlib/zlib.gemspec b/ext/zlib/zlib.gemspec
index 4a77ae325e..ae1f24143d 100644
--- a/ext/zlib/zlib.gemspec
+++ b/ext/zlib/zlib.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Ruby interface for the zlib compression/decompression library}
   spec.description   = %q{Ruby interface for the zlib compression/decompression library}
   spec.homepage      = "https://github.com/ruby/zlib"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses       = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "ext/zlib/extconf.rb", "ext/zlib/zlib.c", "zlib.gemspec"]
   spec.bindir        = "exe"
diff --git a/lib/benchmark/benchmark.gemspec b/lib/benchmark/benchmark.gemspec
index 773cab19b0..031ccbe34a 100644
--- a/lib/benchmark/benchmark.gemspec
+++ b/lib/benchmark/benchmark.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{a performance benchmarking library}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/benchmark"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses       = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/cgi/cgi.gemspec b/lib/cgi/cgi.gemspec
index fbdec5d3d6..1a883934e5 100644
--- a/lib/cgi/cgi.gemspec
+++ b/lib/cgi/cgi.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Support for the Common Gateway Interface protocol.}
   spec.description   = %q{Support for the Common Gateway Interface protocol.}
   spec.homepage      = "https://github.com/ruby/cgi"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
   spec.required_ruby_version = ">= 2.5.0"
 
   spec.metadata["homepage_uri"] = spec.homepage
diff --git a/lib/csv/csv.gemspec b/lib/csv/csv.gemspec
index fee854f514..f555c4efab 100644
--- a/lib/csv/csv.gemspec
+++ b/lib/csv/csv.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = "CSV Reading and Writing"
   spec.description   = "The CSV library provides a complete interface to CSV files and data. It offers tools to enable you to read and write to and from Strings or IO objects, as needed."
   spec.homepage      = "https://github.com/ruby/csv"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   lib_path = "lib"
   spec.require_paths = [lib_path]
diff --git a/lib/delegate/delegate.gemspec b/lib/delegate/delegate.gemspec
index bf7dd6600d..05d9ced175 100644
--- a/lib/delegate/delegate.gemspec
+++ b/lib/delegate/delegate.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Provides three abilities to delegate method calls to an object.}
   spec.description   = %q{Provides three abilities to delegate method calls to an object.}
   spec.homepage      = "https://github.com/ruby/delegate"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/fileutils.gemspec b/lib/fileutils.gemspec
index cd35c09dbc..53c32e7e3e 100644
--- a/lib/fileutils.gemspec
+++ b/lib/fileutils.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
   s.authors = ["Minero Aoki"]
   s.email = [nil]
   s.homepage = "https://github.com/ruby/fileutils"
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 
   s.metadata = {
     "source_code_uri" => "https://github.com/ruby/fileutils"
diff --git a/lib/forwardable/forwardable.gemspec b/lib/forwardable/forwardable.gemspec
index 54e54f4c3c..1d5f6eae63 100644
--- a/lib/forwardable/forwardable.gemspec
+++ b/lib/forwardable/forwardable.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Provides delegation of specified methods to a designated object.}
   spec.description   = %q{Provides delegation of specified methods to a designated object.}
   spec.homepage      = "https://github.com/ruby/forwardable"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = ["forwardable.gemspec", "lib/forwardable.rb", "lib/forwardable/impl.rb", "lib/forwardable/version.rb"]
   spec.bindir        = "exe"
diff --git a/lib/getoptlong/getoptlong.gemspec b/lib/getoptlong/getoptlong.gemspec
index 123977c1f3..9ebe3aed7e 100644
--- a/lib/getoptlong/getoptlong.gemspec
+++ b/lib/getoptlong/getoptlong.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{GetoptLong for Ruby}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/getoptlong"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/ipaddr.gemspec b/lib/ipaddr.gemspec
index 753156af5e..8f8fc4afaa 100644
--- a/lib/ipaddr.gemspec
+++ b/lib/ipaddr.gemspec
@@ -15,7 +15,7 @@ IPAddr provides a set of methods to manipulate an IP address.
 Both IPv4 and IPv6 are supported.
   DESCRIPTION
   spec.homepage      = "https://github.com/ruby/ipaddr"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "ipaddr.gemspec", "lib/ipaddr.rb"]
   spec.bindir        = "exe"
diff --git a/lib/irb/irb.gemspec b/lib/irb/irb.gemspec
index 658fe813f1..d3a4a26ba9 100644
--- a/lib/irb/irb.gemspec
+++ b/lib/irb/irb.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Interactive Ruby command-line tool for REPL (Read Eval Print Loop).}
   spec.description   = %q{Interactive Ruby command-line tool for REPL (Read Eval Print Loop).}
   spec.homepage      = "https://github.com/ruby/irb"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [
     ".document",
diff --git a/lib/logger/logger.gemspec b/lib/logger/logger.gemspec
index 07e0fa16fd..cd6d97de3d 100644
--- a/lib/logger/logger.gemspec
+++ b/lib/logger/logger.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Provides a simple logging utility for outputting messages.}
   spec.description   = %q{Provides a simple logging utility for outputting messages.}
   spec.homepage      = "https://github.com/ruby/logger"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = Dir.glob("lib/**/*.rb") + ["logger.gemspec"]
   spec.bindir        = "exe"
diff --git a/lib/matrix/matrix.gemspec b/lib/matrix/matrix.gemspec
index 018963d913..d2ff9ce7c6 100644
--- a/lib/matrix/matrix.gemspec
+++ b/lib/matrix/matrix.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{An implementation of Matrix and Vector classes.}
   spec.description   = %q{An implementation of Matrix and Vector classes.}
   spec.homepage      = "https://github.com/ruby/matrix"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
   spec.required_ruby_version = ">= 2.5.0"
 
   spec.files         = [".gitignore", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "lib/matrix.rb", "lib/matrix/eigenvalue_decomposition.rb", "lib/matrix/lup_decomposition.rb", "lib/matrix/version.rb", "matrix.gemspec"]
diff --git a/lib/mutex_m.gemspec b/lib/mutex_m.gemspec
index 409ed5b7b2..484db2cacf 100644
--- a/lib/mutex_m.gemspec
+++ b/lib/mutex_m.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Mixin to extend objects to be handled like a Mutex.}
   spec.description   = %q{Mixin to extend objects to be handled like a Mutex.}
   spec.homepage      = "https://github.com/ruby/mutex_m"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "lib/mutex_m.rb", "mutex_m.gemspec"]
   spec.bindir        = "exe"
diff --git a/lib/net/net-pop.gemspec b/lib/net/net-pop.gemspec
index 12e633cc77..911af1c527 100644
--- a/lib/net/net-pop.gemspec
+++ b/lib/net/net-pop.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Ruby client library for POP3.}
   spec.description   = %q{Ruby client library for POP3.}
   spec.homepage      = "https://github.com/ruby/net-pop"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses       = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/net/net-smtp.gemspec b/lib/net/net-smtp.gemspec
index c547beb754..79bc9c7986 100644
--- a/lib/net/net-smtp.gemspec
+++ b/lib/net/net-smtp.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Simple Mail Transfer Protocol client library for Ruby.}
   spec.description   = %q{Simple Mail Transfer Protocol client library for Ruby.}
   spec.homepage      = "https://github.com/ruby/net-smtp"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
   spec.required_ruby_version = ">= 2.5.0"
 
   spec.metadata["homepage_uri"] = spec.homepage
diff --git a/lib/observer/observer.gemspec b/lib/observer/observer.gemspec
index f438f17437..46538e881a 100644
--- a/lib/observer/observer.gemspec
+++ b/lib/observer/observer.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Implementation of the Observer object-oriented design pattern.}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/observer"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/open3/open3.gemspec b/lib/open3/open3.gemspec
index b029c04ee8..72a105a322 100644
--- a/lib/open3/open3.gemspec
+++ b/lib/open3/open3.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Popen, but with stderr, too}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/open3"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/ostruct/ostruct.gemspec b/lib/ostruct/ostruct.gemspec
index e3acace50d..14b0b5e85b 100644
--- a/lib/ostruct/ostruct.gemspec
+++ b/lib/ostruct/ostruct.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Class to build custom data structures, similar to a Hash.}
   spec.description   = %q{Class to build custom data structures, similar to a Hash.}
   spec.homepage      = "https://github.com/ruby/ostruct"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
   spec.required_ruby_version = ">= 2.5.0"
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "lib/ostruct.rb", "lib/ostruct/version.rb", "ostruct.gemspec"]
diff --git a/lib/prime.gemspec b/lib/prime.gemspec
index 74f62e3d9b..86247649df 100644
--- a/lib/prime.gemspec
+++ b/lib/prime.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Prime numbers and factorization library.}
   spec.description   = %q{Prime numbers and factorization library.}
   spec.homepage      = "https://github.com/ruby/prime"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "lib/prime.rb", "prime.gemspec"]
   spec.bindir        = "exe"
diff --git a/lib/pstore/pstore.gemspec b/lib/pstore/pstore.gemspec
index d04fddcb0a..8425795afe 100644
--- a/lib/pstore/pstore.gemspec
+++ b/lib/pstore/pstore.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Transactional File Storage for Ruby Objects}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/pstore"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = "https://github.com/ruby/pstore"
diff --git a/lib/singleton/singleton.gemspec b/lib/singleton/singleton.gemspec
index 2f23233ccf..88d3111b65 100644
--- a/lib/singleton/singleton.gemspec
+++ b/lib/singleton/singleton.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{The Singleton module implements the Singleton pattern.}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/singleton"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/timeout/timeout.gemspec b/lib/timeout/timeout.gemspec
index 12ac062b6d..3dc37f8768 100644
--- a/lib/timeout/timeout.gemspec
+++ b/lib/timeout/timeout.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Auto-terminate potentially long-running operations in Ruby.}
   spec.description   = %q{Auto-terminate potentially long-running operations in Ruby.}
   spec.homepage      = "https://github.com/ruby/timeout"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/tracer/tracer.gemspec b/lib/tracer/tracer.gemspec
index 63e845cf84..a2275d850c 100644
--- a/lib/tracer/tracer.gemspec
+++ b/lib/tracer/tracer.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{Outputs a source level execution trace of a Ruby program.}
   spec.description   = %q{Outputs a source level execution trace of a Ruby program.}
   spec.homepage      = "https://github.com/ruby/tracer"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.files         = [".gitignore", ".travis.yml", "Gemfile", "LICENSE.txt", "README.md", "Rakefile", "bin/console", "bin/setup", "lib/tracer.rb", "lib/tracer/version.rb", "tracer.gemspec"]
   spec.bindir        = "exe"
diff --git a/lib/uri/uri.gemspec b/lib/uri/uri.gemspec
index 95cb8e2d42..c4a16f47eb 100644
--- a/lib/uri/uri.gemspec
+++ b/lib/uri/uri.gemspec
@@ -13,7 +13,7 @@ Gem::Specification.new do |spec|
   spec.summary       = %q{URI is a module providing classes to handle Uniform Resource Identifiers}
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/uri"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage
diff --git a/lib/weakref/weakref.gemspec b/lib/weakref/weakref.gemspec
index 587013a424..acc4e0fbc5 100644
--- a/lib/weakref/weakref.gemspec
+++ b/lib/weakref/weakref.gemspec
@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = "https://github.com/ruby/weakref"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.
diff --git a/lib/webrick/webrick.gemspec b/lib/webrick/webrick.gemspec
index 97e93b5ace..5ede24d7ec 100644
--- a/lib/webrick/webrick.gemspec
+++ b/lib/webrick/webrick.gemspec
@@ -62,7 +62,7 @@ Gem::Specification.new do |s|
   s.authors = ["TAKAHASHI Masayoshi", "GOTOU YUUZOU", "Eric Wong"]
   s.email = [nil, nil, 'normal@ruby-lang.org']
   s.homepage = "https://www.ruby-lang.org"
-  s.license = "BSD-2-Clause"
+  s.licenses = ["Ruby", "BSD-2-Clause"]
 
   if s.respond_to?(:metadata=)
     s.metadata = {
diff --git a/lib/yaml/yaml.gemspec b/lib/yaml/yaml.gemspec
index ba5027a9b6..7b83f355b9 100644
--- a/lib/yaml/yaml.gemspec
+++ b/lib/yaml/yaml.gemspec
@@ -7,7 +7,7 @@ Gem::Specification.new do |spec|
   spec.summary       = "YAML Ain't Markup Language"
   spec.description   = spec.summary
   spec.homepage      = "https://github.com/ruby/yaml"
-  spec.license       = "BSD-2-Clause"
+  spec.licenses      = ["Ruby", "BSD-2-Clause"]
 
   spec.metadata["homepage_uri"] = spec.homepage
   spec.metadata["source_code_uri"] = spec.homepage