diff --git a/bootstrap/_deb_common.sh b/bootstrap/_deb_common.sh
index 71144ce40..4c6b91a33 100755
--- a/bootstrap/_deb_common.sh
+++ b/bootstrap/_deb_common.sh
@@ -44,7 +44,7 @@ apt-get install -y --no-install-recommends \
   libffi-dev \
   ca-certificates \
 
-if ! which virtualenv > /dev/null ; then
+if ! command -v virtualenv > /dev/null ; then
   echo Failed to install a working \"virtualenv\" command, exiting
   exit 1
 fi
diff --git a/letsencrypt-auto b/letsencrypt-auto
index 25c83cc08..44de7fbf2 100755
--- a/letsencrypt-auto
+++ b/letsencrypt-auto
@@ -83,11 +83,11 @@ ExperimentalBootstrap() {
 }
 
 DeterminePythonVersion() {
-  if which python2 > /dev/null ; then
+  if command -v python2 > /dev/null ; then
     export LE_PYTHON=${LE_PYTHON:-python2}
-  elif which python2.7 > /dev/null ; then
+  elif command -v python2.7 > /dev/null ; then
     export LE_PYTHON=${LE_PYTHON:-python2.7}
-  elif which python > /dev/null ; then
+  elif command -v python > /dev/null ; then
     export LE_PYTHON=${LE_PYTHON:-python}
   else
     echo "Cannot find any Pythons... please install one!"