diff --git a/ruby.spec b/ruby.spec
index 18c428f..9cf6d32 100644
--- a/ruby.spec
+++ b/ruby.spec
@@ -92,6 +92,11 @@ Patch12: ruby-1.9.3-mkmf-verbose.patch
 
 Requires: %{name}-libs%{?_isa} = %{version}-%{release}
 Requires: ruby(rubygems) >= %{rubygems_version}
+# Make the bigdecimal gem a runtime dependency of Ruby to avoid problems
+# with user-installed gems, that don't require it in gemspec/Gemfile
+# See https://bugzilla.redhat.com/show_bug.cgi?id=829209
+# and http://bugs.ruby-lang.org/issues/6123
+Requires: rubygem(bigdecimal) >= %{bigdecimal_version}
 
 BuildRequires: autoconf
 BuildRequires: gdbm-devel
@@ -718,6 +723,9 @@ make check TESTS="-v -x test_drbssl.rb -x test_time_tz.rb -x test_httprequest.rb
 
 %changelog
 * Mon Jun 11 2012 Bohuslav Kabrda <bkabrda@redhat.com> - 2.0.0.0-0.1.r35922
+- Make the bigdecimal gem a runtime dependency of Ruby.
+
+* Mon Jun 11 2012 Bohuslav Kabrda <bkabrda@redhat.com> - 2.0.0.0-0.1.r35922
 - Make symlinks for bigdecimal and io-console gems to ruby stdlib dirs (RHBZ 829209).
 
 * Tue May 29 2012 Bohuslav Kabrda <bkabrda@redhat.com> - 2.0.0.0-0.1.r35922