diff --git a/python/inet/test/chart.py b/python/inet/test/chart.py
index 9907e6e9041..0239e28951c 100644
--- a/python/inet/test/chart.py
+++ b/python/inet/test/chart.py
@@ -28,23 +28,15 @@
 
 
 def sewar_rmse(a, b):
-    a,b = sewar_initial_check(a,b)
+    assert a.shape == b.shape, "Supplied images have different sizes " + \
+    str(a.shape) + " and " + str(b.shape)
+    if len(a.shape) == 2:
+        a = a[:,:,numpy.newaxis]
+        b = b[:,:,numpy.newaxis]
+    a = a.astype(numpy.float64)
+    b = b.astype(numpy.float64)
     return numpy.sqrt(numpy.mean((a.astype(numpy.float64)-b.astype(numpy.float64))**2))
 
-def sewar_initial_check(GT,P):
-	assert GT.shape == P.shape, "Supplied images have different sizes " + \
-	str(GT.shape) + " and " + str(P.shape)
-	if GT.dtype != P.dtype:
-		msg = "Supplied images have different dtypes " + \
-			str(GT.dtype) + " and " + str(P.dtype)
-		_logger.warn(msg)
-
-	if len(GT.shape) == 2:
-		GT = GT[:,:,numpy.newaxis]
-		P = P[:,:,numpy.newaxis]
-
-	return GT.astype(numpy.float64),P.astype(numpy.float64)
-
 class ChartTestTask(TestTask):
     def __init__(self, analysis_file_name, id, chart_name, simulation_project=None, name="chart test", **kwargs):
         super().__init__(name=name, **kwargs)
@@ -77,8 +69,12 @@ def run_protected(self, keep_charts=True, output_stream=sys.stdout, **kwargs):
                 if os.path.exists(old_file_name):
                     new_image = matplotlib.image.imread(new_file_name)
                     old_image = matplotlib.image.imread(old_file_name)
+                    if old_image.shape != new_image.shape:
+                        return self.task_result_class(self, result="FAIL", reason="Supplied images have different sizes" + str(old_image.shape) + " and " + str(new_image.shape))
                     metric = sewar_rmse(old_image, new_image)
-                    if metric == 0 or not keep_charts:
+                    if type(metric) == str:
+                        _logger.info(metric)
+                    elif metric == 0 or not keep_charts:
                         os.remove(new_file_name)
                     else:
                         image_diff = numpy.abs(new_image - old_image)
@@ -183,7 +179,10 @@ def run_protected(self, keep_charts=True, **kwargs):
                 if os.path.exists(old_file_name):
                     new_image = matplotlib.image.imread(new_file_name)
                     old_image = matplotlib.image.imread(old_file_name)
-                    metric = sewar_rmse(old_image, new_image)
+                    if old_image.shape != new_image.shape:
+                        metric = 1
+                    else:
+                        metric = sewar_rmse(old_image, new_image)
                     if metric == 0:
                         os.remove(new_file_name)
                     else: