diff --git a/skimage/viewer/canvastools/recttool.py b/skimage/viewer/canvastools/recttool.py
index 93400ceb..da6accf2 100644
--- a/skimage/viewer/canvastools/recttool.py
+++ b/skimage/viewer/canvastools/recttool.py
@@ -53,18 +53,18 @@ class RectangleTool(CanvasToolBase, RectangleSelector):
     >>> ax.imshow(im)
 
     >>> def print_the_rect(extents):
-            global im,ax
-            coord = np.int64(extents)
-            [rr1, cc1] = line(coord[2],coord[0],coord[2],coord[1])
-            [rr2, cc2] = line(coord[2],coord[1],coord[3],coord[1])
-            [rr3, cc3] = line(coord[3],coord[1],coord[3],coord[0])
-            [rr4, cc4] = line(coord[3],coord[0],coord[2],coord[0])
-            set_color(im, (rr1, cc1), [255, 255, 0])
-            set_color(im, (rr2, cc2), [0, 255, 255])
-            set_color(im, (rr3, cc3), [255, 0, 255])
-            set_color(im, (rr4, cc4), [0, 0, 0])
-            ax.imshow(im)
-            plt.show()
+    ...     global im, ax
+    ...     coord = np.int64(extents)
+    ...     [rr1, cc1] = line(coord[2],coord[0],coord[2],coord[1])
+    ...     [rr2, cc2] = line(coord[2],coord[1],coord[3],coord[1])
+    ...     [rr3, cc3] = line(coord[3],coord[1],coord[3],coord[0])
+    ...     [rr4, cc4] = line(coord[3],coord[0],coord[2],coord[0])
+    ...     set_color(im, (rr1, cc1), [255, 255, 0])
+    ...     set_color(im, (rr2, cc2), [0, 255, 255])
+    ...     set_color(im, (rr3, cc3), [255, 0, 255])
+    ...     set_color(im, (rr4, cc4), [0, 0, 0])
+    ...     ax.imshow(im)
+    ...     plt.show()
 
     >>> rect_tool = RectangleTool(ax, on_enter=print_the_rect)
     >>> plt.show()