diff --git a/Gemfile b/Gemfile
index 22fa0843e..da186a0a7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -19,10 +19,19 @@ if RUBY_VERSION >= '2.4' && RUBY_ENGINE == 'ruby'
   gem 'rubocop', "~> 0.52.1"
 end
 
-if RUBY_VERSION < '2.0.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
-  gem 'ffi', '< 1.9.15' # allow ffi to be installed on older rubies on windows
+# allow gems to be installed on older rubies and/or windows
+if RUBY_VERSION < '2.2.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
+  gem 'ffi', '< 1.10'
 elsif RUBY_VERSION < '1.9'
   gem 'ffi', '< 1.9.19' # ffi dropped Ruby 1.8 support in 1.9.19
+elsif RUBY_VERSION < '2.0'
+  gem 'ffi', '< 1.11.0' # ffi dropped Ruby 1.9 support in 1.11.0
+else
+  gem 'ffi', '> 1.9.24' # prevent Github security vulnerability warning
+end
+
+if RUBY_VERSION < '2.2.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
+  gem "childprocess", "< 1.0.0"
 end
 
 ### deps for rdoc.info