diff --git a/scikits/image/io/_plugins/_colormixer.pyx b/scikits/image/io/_plugins/_colormixer.pyx
index 25767f66..2aa2161b 100644
--- a/scikits/image/io/_plugins/_colormixer.pyx
+++ b/scikits/image/io/_plugins/_colormixer.pyx
@@ -139,6 +139,7 @@ def brightness(np.ndarray[np.uint8_t, ndim=3] img,
 
 
 @cython.boundscheck(False)
+@cython.cdivision(True)
 def sigmoid_gamma(np.ndarray[np.uint8_t, ndim=3] img,
                   np.ndarray[np.uint8_t, ndim=3] stateimg,
                   float alpha, float beta):