diff --git a/skimage/feature/corner_cy.pyx b/skimage/feature/corner_cy.pyx
index c810150b..2b010693 100644
--- a/skimage/feature/corner_cy.pyx
+++ b/skimage/feature/corner_cy.pyx
@@ -7,6 +7,7 @@ cimport numpy as cnp
 from libc.float cimport DBL_MAX
 from libc.math cimport atan2
 
+from skimage.util import img_as_float
 from skimage.color import rgb2grey
 
 from .util import _prepare_grayscale_input_2D