diff --git a/ext/openssl/deprecation.rb b/ext/openssl/deprecation.rb
index 6af7d562fb..fdf2d30ed0 100644
--- a/ext/openssl/deprecation.rb
+++ b/ext/openssl/deprecation.rb
@@ -12,6 +12,10 @@ module OpenSSL
     flag
   end
 
+  def self.restore_warning_flag
+    $warnflags = @warnflags
+  end
+
   def self.check_func(func, header)
     have_func(func, header, deprecated_warning_flag)
   end
diff --git a/ext/openssl/extconf.rb b/ext/openssl/extconf.rb
index 344d759652..87a682b4ab 100644
--- a/ext/openssl/extconf.rb
+++ b/ext/openssl/extconf.rb
@@ -19,7 +19,7 @@ dir_config("kerberos")
 
 Logging::message "=== OpenSSL for Ruby configurator ===\n"
 
-# Add -Werror=deprecated-declarations to $warnflags if available
+# Check with -Werror=deprecated-declarations if available
 OpenSSL.deprecated_warning_flag
 
 ##
@@ -185,5 +185,6 @@ have_func("SSL_CTX_set_post_handshake_auth")
 Logging::message "=== Checking done. ===\n"
 
 create_header
+OpenSSL.restore_warning_flag
 create_makefile("openssl")
 Logging::message "Done.\n"