diff --git a/ruby.spec b/ruby.spec
index 118ca77..2a314ec 100644
--- a/ruby.spec
+++ b/ruby.spec
@@ -308,6 +308,9 @@ Summary:    The Interactive Ruby
 Version:    %{irb_version}
 Requires:   ruby(release)
 Requires:   ruby(rubygems) >= %{rubygems_version}
+# ruby-default-gems is required to run irb.
+# https://bugs.ruby-lang.org/issues/16951
+Requires:   ruby-default-gems >= %{ruby_version}
 Provides:   irb = %{version}-%{release}
 Provides:   rubygem(irb) = %{version}-%{release}
 # Obsoleted by Ruby 2.6 in F30 timeframe.
@@ -1308,6 +1311,7 @@ make check TESTS="-v $DISABLE_TESTS" MSPECOPT="-fs $MSPECOPTS"
 * Fri Jun 26 2020 Vít Ondruch <vondruch@redhat.com> - 2.7.1-133
 - Fix `require` behavior allowing to load libraries multiple times.
   Resolves: rhbz#1842989
+- Add ruby-default-gems dependency on irb.
 
 * Fri Jun 26 2020 Jun Aruga <jaruga@redhat.com> - 2.7.1-133
 - Ship racc binary.