diff --git a/letsencrypt-auto-source/letsencrypt-auto b/letsencrypt-auto-source/letsencrypt-auto
index 84f46f537..1c6c53717 100755
--- a/letsencrypt-auto-source/letsencrypt-auto
+++ b/letsencrypt-auto-source/letsencrypt-auto
@@ -892,7 +892,7 @@ TempDir() {
 # Returns 0 if a letsencrypt installation exists at $OLD_VENV_PATH, otherwise,
 # returns a non-zero number.
 OldVenvExists() {
-    [ -z "$OLD_VENV_PATH" -o ! -f "$OLD_VENV_PATH/bin/letsencrypt" ]
+    [ -n "$OLD_VENV_PATH" -a -f "$OLD_VENV_PATH/bin/letsencrypt" ]
 }
 
 if [ "$1" = "--le-auto-phase2" ]; then
@@ -1421,7 +1421,7 @@ else
   # package). Phase 2 checks the version of the locally installed certbot.
 
   if [ ! -f "$VENV_BIN/letsencrypt" ]; then
-    if OldVenvExists; then
+    if ! OldVenvExists; then
       if [ "$HELP" = 1 ]; then
         echo "$USAGE"
         exit 0
diff --git a/letsencrypt-auto-source/letsencrypt-auto.template b/letsencrypt-auto-source/letsencrypt-auto.template
index 6c1a0026b..e922f324f 100755
--- a/letsencrypt-auto-source/letsencrypt-auto.template
+++ b/letsencrypt-auto-source/letsencrypt-auto.template
@@ -431,7 +431,7 @@ TempDir() {
 # Returns 0 if a letsencrypt installation exists at $OLD_VENV_PATH, otherwise,
 # returns a non-zero number.
 OldVenvExists() {
-    [ -z "$OLD_VENV_PATH" -o ! -f "$OLD_VENV_PATH/bin/letsencrypt" ]
+    [ -n "$OLD_VENV_PATH" -a -f "$OLD_VENV_PATH/bin/letsencrypt" ]
 }
 
 if [ "$1" = "--le-auto-phase2" ]; then
@@ -580,7 +580,7 @@ else
   # package). Phase 2 checks the version of the locally installed certbot.
 
   if [ ! -f "$VENV_BIN/letsencrypt" ]; then
-    if OldVenvExists; then
+    if ! OldVenvExists; then
       if [ "$HELP" = 1 ]; then
         echo "$USAGE"
         exit 0