diff --git a/ext/Setup b/ext/Setup
index ac79c86f84..0376e2fc6c 100644
--- a/ext/Setup
+++ b/ext/Setup
@@ -33,7 +33,6 @@
 #rbconfig/sizeof
 #readline
 #ripper
-#sdbm
 #socket
 #stringio
 #strscan
diff --git a/ext/Setup.atheos b/ext/Setup.atheos
index 90a7d01348..3f6263b1e2 100644
--- a/ext/Setup.atheos
+++ b/ext/Setup.atheos
@@ -20,7 +20,6 @@ pty
 racc/parse
 readline
 ripper
-sdbm
 socket
 stringio
 strscan
diff --git a/ext/Setup.nt b/ext/Setup.nt
index fb5989b87f..dc36aa8688 100644
--- a/ext/Setup.nt
+++ b/ext/Setup.nt
@@ -21,7 +21,6 @@ nkf
 racc/cparse
 #readline
 #ripper
-sdbm
 socket
 stringio
 strscan
diff --git a/misc/expand_tabs.rb b/misc/expand_tabs.rb
index 7b3bff78ff..b091fecda7 100755
--- a/misc/expand_tabs.rb
+++ b/misc/expand_tabs.rb
@@ -96,7 +96,6 @@ DEFAULT_GEM_EXTS = %w[
   json
   openssl
   psych
-  sdbm
   stringio
   strscan
   zlib
diff --git a/test/test_extlibs.rb b/test/test_extlibs.rb
index 7dc22ee8a3..1d11dbe2e0 100644
--- a/test/test_extlibs.rb
+++ b/test/test_extlibs.rb
@@ -71,7 +71,6 @@ class TestExtLibs < Test::Unit::TestCase
   check_existence "rbconfig/sizeof"
   #check_existence "readline" # depend on libreadline
   check_existence "ripper"
-  check_existence "sdbm"
   check_existence "socket"
   check_existence "stringio"
   check_existence "strscan"
diff --git a/tool/sync_default_gems.rb b/tool/sync_default_gems.rb
index 4605bf9aea..9721b44a1d 100644
--- a/tool/sync_default_gems.rb
+++ b/tool/sync_default_gems.rb
@@ -13,7 +13,6 @@
 # * https://github.com/ruby/webrick
 # * https://github.com/ruby/dbm
 # * https://github.com/ruby/gdbm
-# * https://github.com/ruby/sdbm
 # * https://github.com/ruby/etc
 # * https://github.com/ruby/date
 # * https://github.com/ruby/zlib
@@ -74,7 +73,6 @@ $repositories = {
   webrick: 'ruby/webrick',
   dbm: 'ruby/dbm',
   gdbm: 'ruby/gdbm',
-  sdbm: 'ruby/sdbm',
   etc: 'ruby/etc',
   date: 'ruby/date',
   zlib: 'ruby/zlib',
@@ -201,12 +199,6 @@ def sync_default_gems(gem)
     cp_r("#{upstream}/test/gdbm", "test")
     cp_r("#{upstream}/gdbm.gemspec", "ext/gdbm")
     `git checkout ext/gdbm/depend ext/gdbm/README`
-  when "sdbm"
-    rm_rf(%w[ext/sdbm test/sdbm])
-    cp_r("#{upstream}/ext/sdbm", "ext")
-    cp_r("#{upstream}/test/sdbm", "test")
-    cp_r("#{upstream}/sdbm.gemspec", "ext/sdbm")
-    `git checkout ext/sdbm/depend`
   when "etc"
     rm_rf(%w[ext/etc test/etc])
     cp_r("#{upstream}/ext/etc", "ext")