diff --git a/skimage/filter/rank/generic_cy.pyx b/skimage/filter/rank/generic_cy.pyx
index 2953b2f0..dd461fc7 100644
--- a/skimage/filter/rank/generic_cy.pyx
+++ b/skimage/filter/rank/generic_cy.pyx
@@ -222,9 +222,9 @@ cdef inline double _kernel_pop(Py_ssize_t* histo, double pop, dtype_t g,
     return pop
 
 cdef inline double _kernel_sum(Py_ssize_t* histo, double pop,dtype_t g,
-                                Py_ssize_t max_bin, Py_ssize_t mid_bin,
-                                double p0, double p1,
-                                Py_ssize_t s0, Py_ssize_t s1):
+                               Py_ssize_t max_bin, Py_ssize_t mid_bin,
+                               double p0, double p1,
+                               Py_ssize_t s0, Py_ssize_t s1):
 
     cdef Py_ssize_t i
     cdef Py_ssize_t sum = 0