diff --git a/plugins/ps/functions b/plugins/ps/functions
index 48f9ed7cb..d550b8bdd 100755
--- a/plugins/ps/functions
+++ b/plugins/ps/functions
@@ -92,11 +92,14 @@ set_scale() {
   local DOKKU_PROCFILE="$DOKKU_ROOT/$APP/DOKKU_PROCFILE"
   shift 1
 
+  extract_procfile "$APP" "$IMAGE_TAG" > /dev/null
+  trap 'remove_procfile $APP' RETURN INT TERM EXIT
+
   local SCALE_SETTINGS=("$@")
   for procscale in "${SCALE_SETTINGS[@]}"; do
     local PROC_NAME=${procscale%%=*}
     local PROC_COUNT=${procscale#*=}
-    if [[ -f "$DOKKU_PROCFILE" ]] && ! procfile-util exists --procfile "$DOKKU_PROCFILE" --process-type "$PROC_NAME" > /dev/null 2>&1; then
+    if [[ -f "$DOKKU_PROCFILE" ]] && ! procfile-util exists --procfile "$DOKKU_SCALE_FILE" --process-type "$PROC_NAME" > /dev/null 2>&1; then
       dokku_log_fail "${PROC_NAME} is not a valid process name"
     fi
     is_number "$PROC_COUNT" || dokku_log_fail "ps:scale $PROC_COUNT is not a number"
diff --git a/tests/unit/10_ps-dockerfile.bats b/tests/unit/10_ps-dockerfile.bats
index 513c32141..cd7329c6f 100644
--- a/tests/unit/10_ps-dockerfile.bats
+++ b/tests/unit/10_ps-dockerfile.bats
@@ -71,7 +71,7 @@ teardown() {
 }
 
 @test "(ps:scale) dockerfile non-existent process" {
-  run bash -c "dokku ps:scale $TEST_APP non-existent=2"
+  run bash -c "dokku --trace ps:scale $TEST_APP non-existent=2"
   echo "output: "$output
   echo "status: "$status
   assert_failure