diff --git a/bob/ip/qualitymeasure/msu_iqa_features.py b/bob/ip/qualitymeasure/msu_iqa_features.py
index 87abc1efd3c4aad7b59daf083992236e0cca46e5..8b46cff65df80d440c5d93be950dd3a97c3d7418 100644
--- a/bob/ip/qualitymeasure/msu_iqa_features.py
+++ b/bob/ip/qualitymeasure/msu_iqa_features.py
@@ -65,10 +65,10 @@ def sobelEdgeMap(image, orientation='both'):
     refSobel_sep = bob.ip.base.sobel(refImage)
     refSobelX = refSobel_sep[0, :, :]
     refSobelY = refSobel_sep[1, :, :]
-    if orientation is 'horizontal':
+    if orientation == 'horizontal':
         refEdge = iqm.edge_thinning(refSobelX[:, :], refSobelX[:, :], thinning)
     else:
-        if orientation is 'vertical':
+        if orientation == 'vertical':
             refEdge = iqm.edge_thinning(
                 refSobelY[
                     :, :], refSobelY[