diff --git a/tools/git-step-rebase b/tools/git-step-rebase
index d19414e..33eff41 100755
--- a/tools/git-step-rebase
+++ b/tools/git-step-rebase
@@ -41,7 +41,7 @@ COMMON_PARENT=$(git merge-base HEAD ${BASE_BRANCH})
 echo
 echo "Common parent is ${COMMON_PARENT}."
 
-PARENTS=$(git rev-list ${COMMON_PARENT}..${BASE_BRANCH} | wc -l)
+PARENTS=$(git rev-list --first-parent ${COMMON_PARENT}..${BASE_BRANCH} | wc -l)
 echo "${PARENTS} commits to go."
 let PARENTS=${PARENTS}-1