diff --git a/rubygem-ruby-debug-base19.spec b/rubygem-ruby-debug-base19.spec
index d8ff95f..41562d4 100644
--- a/rubygem-ruby-debug-base19.spec
+++ b/rubygem-ruby-debug-base19.spec
@@ -105,6 +105,7 @@ cp -p ruby-%{ruby_fullver}/{*.h,*.inc} ruby_headers/
 rm -rf ruby-%{ruby_fullver}/
 
 %build
+export CONFIGURE_ARGS="--with-cflags=\"%{optflags} -I$(pwd)/ruby_headers\""
 %gem_install
 
 %install