diff --git a/tests/test_imagewrapper.py b/tests/test_imagewrapper.py
index 61ed5c21bbdbccef14f769b4547f9fdb8c6fd8a4..65c790ce3f41300b13cc1dfec07b6f93c8a2e0dd 100644
--- a/tests/test_imagewrapper.py
+++ b/tests/test_imagewrapper.py
@@ -906,8 +906,8 @@ def _test_ImageWrapper_write_in_overlap(niters, seed, threaded):
                 # on this copy
                 expCovSlice = [slice(int(lo), int(hi)) for lo, hi in expCov.T]
 
-                expLo = expData[expCovSlice].min()
-                expHi = expData[expCovSlice].max()
+                expLo = expData[tuple(expCovSlice)].min()
+                expHi = expData[tuple(expCovSlice)].max()
 
                 wrapper[tuple(sliceobjs)] = newData
                 _ImageWraper_busy_wait(wrapper)