diff --git a/skimage/filter/rank/bilateral_rank.pyx b/skimage/filter/rank/bilateral_rank.pyx
index 04f6cb35..e2a1fcf3 100644
--- a/skimage/filter/rank/bilateral_rank.pyx
+++ b/skimage/filter/rank/bilateral_rank.pyx
@@ -36,7 +36,7 @@ __all__ = ['bilateral_mean', 'bilateral_pop']
 
 
 def _apply(func8, func16, image, selem, out, mask, shift_x, shift_y, s0, s1):
-    selem = img_as_ubyte(selem)
+    selem = img_as_ubyte(selem > 0)
     image = np.ascontiguousarray(image)
 
     if mask is None:
diff --git a/skimage/filter/rank/percentile_rank.pyx b/skimage/filter/rank/percentile_rank.pyx
index 7deae623..9db81bcc 100644
--- a/skimage/filter/rank/percentile_rank.pyx
+++ b/skimage/filter/rank/percentile_rank.pyx
@@ -35,7 +35,7 @@ __all__ = ['percentile_autolevel', 'percentile_gradient',
 
 
 def _apply(func8, func16, image, selem, out, mask, shift_x, shift_y, p0, p1):
-    selem = img_as_ubyte(selem)
+    selem = img_as_ubyte(selem > 0)
     image = np.ascontiguousarray(image)
 
     if mask is None:
diff --git a/skimage/filter/rank/rank.pyx b/skimage/filter/rank/rank.pyx
index 5380363a..2ef5484e 100644
--- a/skimage/filter/rank/rank.pyx
+++ b/skimage/filter/rank/rank.pyx
@@ -28,7 +28,7 @@ __all__ = ['autolevel', 'bottomhat', 'equalize', 'gradient', 'maximum', 'mean',
 
 
 def _apply(func8, func16, image, selem, out, mask, shift_x, shift_y):
-    selem = img_as_ubyte(selem)
+    selem = img_as_ubyte(selem > 0)
     image = np.ascontiguousarray(image)
 
     if mask is None: