diff --git a/rubygem-nio4r.spec b/rubygem-nio4r.spec
index a072de5..5dbadd0 100644
--- a/rubygem-nio4r.spec
+++ b/rubygem-nio4r.spec
@@ -3,7 +3,7 @@
 
 Name: rubygem-%{gem_name}
 Version: 1.2.1
-Release: 4%{?dist}
+Release: 5%{?dist}
 Summary: New IO for Ruby
 Group: Development/Languages
 # The entire source code is MIT, bundled libev is BSD or GPLv2+
@@ -49,6 +49,11 @@ gem spec %{SOURCE0} -l --ruby > %{gem_name}.gemspec
 # Create the gem as gem install only works on a gem file
 gem build %{gem_name}.gemspec
 
+# Update %%optflags used in %%gem_install to avoid strict-aliasing warnings.
+# https://github.com/socketry/nio4r/pull/130
+# http://pkgs.fedoraproject.org/cgit/rpms/rubygems.git/tree/macros.rubygems
+%global optflags %{?optflags} -fno-strict-aliasing
+
 # %%gem_install compiles any C extensions and installs the gem into ./%%gem_dir
 # by default, so that we can move it into the buildroot in %%install
 %gem_install
@@ -107,6 +112,9 @@ popd
 %{gem_instdir}/spec
 
 %changelog
+* Tue Feb 21 2017 Jun Aruga <jaruga@redhat.com> - 1.2.1-5
+- Add flag to avoid warnings from strict-aliasing optimization.
+
 * Sat Feb 11 2017 Fedora Release Engineering <releng@fedoraproject.org> - 1.2.1-4
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_26_Mass_Rebuild
 
diff --git a/sources b/sources
index 69e8266..975bd85 100644
--- a/sources
+++ b/sources
@@ -1 +1 @@
-3e3c7bbfc42a8ca412b5eade7d38d0ab  nio4r-1.2.1.gem
+SHA512 (nio4r-1.2.1.gem) = 3136863955bd6f4d489955bae9baf2fb527447c0e71dade1a05402f3e7c8570bf1dd9b8335d70d7303ec4df0a236b13e4ede74ce9154be00a108afcd7c6b7f40