diff --git a/tools/dev/bin/cell-build b/tools/dev/bin/cell-build
index 0a100d7..5dacfe7 100755
--- a/tools/dev/bin/cell-build
+++ b/tools/dev/bin/cell-build
@@ -27,7 +27,7 @@
 
 # Check arguments and environment
 branch=${branch:-origin/master}
-baseCommit=${1:-$(git log | grep $branch | head -n1 | cut -d\  -f2)}
+baseCommit=$(git log -n 1 --pretty=format:"%H" $branch)
 
 # Create a patch file
 git diff $baseCommit > /tmp/$baseCommit.patch