diff --git a/c_mpos/breakout/build.sh b/c_mpos/breakout/build.sh
index 3086e9b3..63261115 100755
--- a/c_mpos/breakout/build.sh
+++ b/c_mpos/breakout/build.sh
@@ -1,6 +1,6 @@
 . ~/.espressif/python_env/idf5.4_py3.11_env/bin/activate
 
-pip install pyelftools
+pip install pyelftools ar
 
 mydir=$(readlink -f "$0")
 mydir=$(dirname "$mydir")