diff --git a/scikits/image/opencv/opencv_cv.pyx b/scikits/image/opencv/opencv_cv.pyx
index 6b28174b..d02f1507 100644
--- a/scikits/image/opencv/opencv_cv.pyx
+++ b/scikits/image/opencv/opencv_cv.pyx
@@ -1821,7 +1821,7 @@ def cvCvtColor(np.ndarray src, int code):
     cdef int out_channels = <int>conversion_params[1]
     src_dtypes = conversion_params[2]
 
-    assert_nchannels(src, src_channels)
+    assert_nchannels(src, [src_channels])
     assert_dtype(src, src_dtypes)
 
     cdef np.ndarray out