diff --git a/orangecontrib/spectroscopy/tests/test_owhyper.py b/orangecontrib/spectroscopy/tests/test_owhyper.py
index 84f0254f5..1ca23cb76 100644
--- a/orangecontrib/spectroscopy/tests/test_owhyper.py
+++ b/orangecontrib/spectroscopy/tests/test_owhyper.py
@@ -123,7 +123,7 @@ def setUpClass(cls):
         # dataset without any attributes, but XY
         whitelight0 = cls.whitelight.transform(
             Orange.data.Domain([], None, metas=cls.whitelight.domain.metas))[:100]
-        unknowns = cls.iris.copy()
+        unknowns = cls.iris[::10].copy()
         with unknowns.unlocked():
             unknowns.X[:, :] = float("nan")
         single_pixel = cls.iris[:50]  # all image coordinates map to one spot