diff --git a/dap/algos/roi.py b/dap/algos/roi.py
index 6f585ee..1420fe5 100644
--- a/dap/algos/roi.py
+++ b/dap/algos/roi.py
@@ -1,10 +1,25 @@
 import numpy as np
 
 
-def calc_roi(results, data, roi_x1, roi_x2, roi_y1, roi_y2, pixel_mask_pf, threshold_value_choice):
+def calc_roi(results, data, pixel_mask_pf, threshold_value_choice):
     if pixel_mask_pf is None:
         return
 
+    for k in ("roi_x1", "roi_x2", "roi_y1", "roi_y2"):
+        if k not in results:
+            return
+
+    roi_x1 = results["roi_x1"]
+    roi_x2 = results["roi_x2"]
+    roi_y1 = results["roi_y1"]
+    roi_y2 = results["roi_y2"]
+
+    if len(roi_x1) == 0:
+        return
+
+    if not (len(roi_x1) == len(roi_x2) == len(roi_y1) == len(roi_y2)):
+        return
+
     roi_results = [0] * len(roi_x1)
     roi_results_normalised = [0] * len(roi_x1)
 
diff --git a/dap/worker.py b/dap/worker.py
index 2c9d9f6..614b096 100644
--- a/dap/worker.py
+++ b/dap/worker.py
@@ -196,13 +196,9 @@ def work(backend_address, accumulator_host, accumulator_port, visualisation_host
                 pfdata[pfdata > threshold_max] = threshold_value
 
     # if roi calculation request is present, make it
-        roi_x1 = results.get("roi_x1", [])
-        roi_x2 = results.get("roi_x2", [])
-        roi_y1 = results.get("roi_y1", [])
-        roi_y2 = results.get("roi_y2", [])
-
-        if len(roi_x1) > 0 and len(roi_x1) == len(roi_x2) == len(roi_y1) == len(roi_y2):
-            calc_roi(results, pfdata, roi_x1, roi_x2, roi_y1, roi_y2, pixel_mask_pf, threshold_value_choice)
+        do_roi = ("roi_x1" in results)
+        if do_roi:
+            calc_roi(results, pfdata, pixel_mask_pf, threshold_value_choice)
 
 # SPI analysis
         do_spi_analysis = results.get("do_spi_analysis", False)