diff --git a/script/build-runtime b/script/build-runtime
index 881b48e9..e302b625 100755
--- a/script/build-runtime
+++ b/script/build-runtime
@@ -9,6 +9,8 @@ fi
 
 ${CC}                   \
   -c                    \
+  -O3                   \
+  -std=c99              \
   -I src                \
   -I include            \
   -I externals/utf8proc \