diff --git a/README.md b/README.md
index 3c32cc0..4bfb47b 100644
--- a/README.md
+++ b/README.md
@@ -111,4 +111,8 @@ by doing following steps:
 
 - Go to Gnat runtime directory {gnat's prefix}/arm-eabi/lib/gnat
 - Copy runtime: `cp -r light-stm32f4 light-stm32f401`
-- Apply patch: `patch light-stm32f401 < {patch dir}/light-stm32f401.patch
+- Apply patch: `patch -p1 -d light-stm32f401 < {patch dir}/light-stm32f401.patch
+- Go to runtime dir: `cd light-stm32f401`
+- Clean: `gprclean -P runtime_build.gpr`
+- Compile runtime: `gprbuild -P runtime_build.gpr`
+