diff --git a/build.sh b/build.sh
index 7cb97a6..22eea20 100755
--- a/build.sh
+++ b/build.sh
@@ -6,7 +6,7 @@ set -euo pipefail
 HERE="$(cd "$(dirname "$0")" && pwd)"
 cd "$HERE"
 
-VERSION="$(grep -oP '__version__\s*=\s*"\K[^"]+' repoman.py)"
+VERSION="$(sed -n 's/^__version__[[:space:]]*=[[:space:]]*"\([^"]*\)".*/\1/p' repoman.py | head -n1)"
 if [ -z "$VERSION" ]; then
   echo "[build] no se pudo leer __version__ de repoman.py" >&2
   exit 1