diff --git a/lib/rubygems/ext/builder.rb b/lib/rubygems/ext/builder.rb
index 581d420bc4..974e1799a1 100644
--- a/lib/rubygems/ext/builder.rb
+++ b/lib/rubygems/ext/builder.rb
@@ -6,6 +6,7 @@
 #++
 
 require 'rubygems/user_interaction'
+require "open3"
 
 class Gem::Ext::Builder
 
@@ -67,13 +68,11 @@ class Gem::Ext::Builder
       results << "current directory: #{Dir.pwd}"
       results << (command.respond_to?(:shelljoin) ? command.shelljoin : command)
 
-      redirections = verbose ? {} : {err: [:child, :out]}
-      IO.popen(command, "r", redirections) do |io|
-        if verbose
-          IO.copy_stream(io, $stdout)
-        else
-          results << io.read
-        end
+      output, status = Open3.capture2e(*command)
+      if verbose
+        puts output
+      else
+        results << output
       end
     rescue => error
       raise Gem::InstallError, "#{command_name || class_name} failed#{error.message}"
@@ -81,14 +80,18 @@ class Gem::Ext::Builder
       ENV['RUBYGEMS_GEMDEPS'] = rubygems_gemdeps
     end
 
-    unless $?.success?
+    unless status.success?
       results << "Building has failed. See above output for more information on the failure." if verbose
+    end
 
+    yield(status, results) if block_given?
+
+    unless status.success?
       exit_reason =
-        if $?.exited?
-          ", exit code #{$?.exitstatus}"
-        elsif $?.signaled?
-          ", uncaught signal #{$?.termsig}"
+        if status.exited?
+          ", exit code #{status.exitstatus}"
+        elsif status.signaled?
+          ", uncaught signal #{status.termsig}"
         end
 
       raise Gem::InstallError, "#{command_name || class_name} failed#{exit_reason}"
diff --git a/lib/rubygems/ext/ext_conf_builder.rb b/lib/rubygems/ext/ext_conf_builder.rb
index 169da438ba..9068f9a5df 100644
--- a/lib/rubygems/ext/ext_conf_builder.rb
+++ b/lib/rubygems/ext/ext_conf_builder.rb
@@ -45,15 +45,15 @@ class Gem::Ext::ExtConfBuilder < Gem::Ext::Builder
         cmd.push(*args)
 
         begin
-          run cmd, results
-        ensure
-          if File.exist? 'mkmf.log'
-            unless $?.success?
-              results << "To see why this extension failed to compile, please check" \
-                " the mkmf.log which can be found here:\n"
-              results << "  " + File.join(dest_path, 'mkmf.log') + "\n"
+          run(cmd, results) do |status, results|
+            if File.exist? 'mkmf.log'
+              unless status.success?
+                results << "To see why this extension failed to compile, please check" \
+                  " the mkmf.log which can be found here:\n"
+                results << "  " + File.join(dest_path, 'mkmf.log') + "\n"
+              end
+              FileUtils.mv 'mkmf.log', dest_path
             end
-            FileUtils.mv 'mkmf.log', dest_path
           end
           siteconf.unlink
         end