diff --git a/invesalius_cy/cy_mesh.pyx b/invesalius_cy/cy_mesh.pyx
index 6d074f8..4c8b605 100644
--- a/invesalius_cy/cy_mesh.pyx
+++ b/invesalius_cy/cy_mesh.pyx
@@ -1,4 +1,5 @@
 # distutils: language = c++
+# cython: language_level=3str
 #cython: boundscheck=False
 #cython: wraparound=False
 #cython: initializedcheck=False
@@ -21,7 +22,7 @@ from libcpp cimport bool
 from libcpp.deque cimport deque as cdeque
 from cython.parallel import prange
 
-from cy_my_types cimport vertex_t, normal_t, vertex_id_t
+from .cy_my_types cimport vertex_t, normal_t, vertex_id_t
 
 import numpy as np
 import vtk
@@ -451,16 +452,16 @@ def ca_smoothing(Mesh mesh, double T, double tmax, double bmin, int n_iters):
 
     t0 = time.time()
     cdef vector[vertex_id_t]* vertices_staircase =  find_staircase_artifacts(mesh, stack_orientation, T)
-    print "vertices staircase", time.time() - t0
+    print("vertices staircase", time.time() - t0)
 
     t0 = time.time()
     cdef vector[weight_t]* weights = calc_artifacts_weight(mesh, deref(vertices_staircase), tmax, bmin)
-    print "Weights", time.time() - t0
+    print("Weights", time.time() - t0)
 
     del vertices_staircase
 
     t0 = time.time()
     taubin_smooth(mesh, deref(weights), 0.5, -0.53, n_iters)
-    print "taubin", time.time() - t0
+    print("taubin", time.time() - t0)
 
     del weights
diff --git a/invesalius_cy/floodfill.pyx b/invesalius_cy/floodfill.pyx
index 6636cc9..4183459 100644
--- a/invesalius_cy/floodfill.pyx
+++ b/invesalius_cy/floodfill.pyx
@@ -1,3 +1,5 @@
+#cython: language_level=3str
+
 import numpy as np
 cimport numpy as np
 cimport cython
@@ -10,7 +12,7 @@ from libcpp cimport bool
 from libcpp.deque cimport deque as cdeque
 from libcpp.vector cimport vector
 
-from cy_my_types cimport image_t, mask_t
+from .cy_my_types cimport image_t, mask_t
 
 cdef struct s_coord:
     int x
@@ -117,9 +119,9 @@ def floodfill_threshold(np.ndarray[image_t, ndim=3] data, list seeds, int t0, in
     cdef cdeque[coord] stack
     cdef coord c
 
-    offset_z = odz / 2
-    offset_y = ody / 2
-    offset_x = odx / 2
+    offset_z = odz // 2
+    offset_y = ody // 2
+    offset_x = odx // 2
 
     for i, j, k in seeds:
         if data[k, j, i] >= t0 and data[k, j, i] <= t1:
@@ -191,13 +193,13 @@ def floodfill_auto_threshold(np.ndarray[image_t, ndim=3] data, list seeds, float
     for i, j, k in seeds:
         append_queue(stack, i, j, k, d, h, w)
         out[k, j, i] = fill
-        print i, j, k, d, h, w
+        print(i, j, k, d, h, w)
 
     with nogil:
         while stack.size():
             pop_queue(stack, &x, &y, &z, d, h, w)
 
-            #  print x, y, z, d, h, w
+            #  print(x, y, z, d, h, w)
 
             xo = x
             yo = y
diff --git a/invesalius_cy/interpolation.pyx b/invesalius_cy/interpolation.pyx
index 9f44648..a314d32 100644
--- a/invesalius_cy/interpolation.pyx
+++ b/invesalius_cy/interpolation.pyx
@@ -1,3 +1,4 @@
+#cython: language_level=3str
 # from interpolation cimport interpolate
 
 import numpy as np
diff --git a/invesalius_cy/mips.pyx b/invesalius_cy/mips.pyx
index 6b0e0a2..93b2641 100644
--- a/invesalius_cy/mips.pyx
+++ b/invesalius_cy/mips.pyx
@@ -1,3 +1,5 @@
+#cython: language_level=3str
+
 #http://en.wikipedia.org/wiki/Local_maximum_intensity_projection
 import numpy as np
 cimport numpy as np
@@ -90,8 +92,8 @@ def lmip(np.ndarray[DTYPE16_t, ndim=3] image, int axis, DTYPE16_t tmin,
 
 cdef DTYPE16_t get_colour(DTYPE16_t vl, DTYPE16_t wl, DTYPE16_t ww):
     cdef DTYPE16_t out_colour
-    cdef DTYPE16_t min_value = wl - (ww / 2)
-    cdef DTYPE16_t max_value = wl + (ww / 2)
+    cdef DTYPE16_t min_value = wl - (ww // 2)
+    cdef DTYPE16_t max_value = wl + (ww // 2)
     if vl < min_value:
         out_colour = min_value
     elif vl > max_value:
@@ -105,8 +107,8 @@ cdef DTYPE16_t get_colour(DTYPE16_t vl, DTYPE16_t wl, DTYPE16_t ww):
 @cython.cdivision(True)
 cdef float get_opacity(DTYPE16_t vl, DTYPE16_t wl, DTYPE16_t ww) nogil:
     cdef float out_opacity
-    cdef DTYPE16_t min_value = wl - (ww / 2)
-    cdef DTYPE16_t max_value = wl + (ww / 2)
+    cdef DTYPE16_t min_value = wl - (ww // 2)
+    cdef DTYPE16_t max_value = wl + (ww // 2)
     if vl < min_value:
         out_opacity = 0.0
     elif vl > max_value:
@@ -120,8 +122,8 @@ cdef float get_opacity(DTYPE16_t vl, DTYPE16_t wl, DTYPE16_t ww) nogil:
 @cython.cdivision(True)
 cdef float get_opacity_f32(DTYPEF32_t vl, DTYPE16_t wl, DTYPE16_t ww) nogil:
     cdef float out_opacity
-    cdef DTYPE16_t min_value = wl - (ww / 2)
-    cdef DTYPE16_t max_value = wl + (ww / 2)
+    cdef DTYPE16_t min_value = wl - (ww // 2)
+    cdef DTYPE16_t max_value = wl + (ww // 2)
     if vl < min_value:
         out_opacity = 0.0
     elif vl > max_value:
@@ -144,8 +146,8 @@ def mida(np.ndarray[DTYPE16_t, ndim=3] image, int axis, DTYPE16_t wl,
     cdef DTYPE16_t max = image.max()
     cdef DTYPE16_t vl
 
-    cdef DTYPE16_t min_value = wl - (ww / 2)
-    cdef DTYPE16_t max_value = wl + (ww / 2)
+    cdef DTYPE16_t min_value = wl - (ww // 2)
+    cdef DTYPE16_t max_value = wl + (ww // 2)
 
     cdef float fmax=0.0
     cdef float fpi
diff --git a/invesalius_cy/transforms.pyx b/invesalius_cy/transforms.pyx
index 5c746d2..8c2c10a 100644
--- a/invesalius_cy/transforms.pyx
+++ b/invesalius_cy/transforms.pyx
@@ -1,3 +1,5 @@
+#cython: language_level=3str
+
 import numpy as np
 cimport numpy as np
 cimport cython
--
libgit2 0.21.2