diff --git a/rover.fnl b/rover.fnl
index eac964e..14ccabd 100644
--- a/rover.fnl
+++ b/rover.fnl
@@ -141,6 +141,10 @@
         (execute (rover 0 45 :e) [:f])
         (where {:x x } (< (math.abs (- x 1.4141)) 0.001)))
 
+(expect "At 45 degrees latitude south, one unit of drive is (sqrt 2) degrees"
+        (execute (rover 0 -45 :e) [:f])
+        (where {:x x :y -45} (< (math.abs (- x 1.4141)) 0.001)))
+
 ;; valid longitudes are -180 .. 180
 
 (expect "Longitude wraps from positive to  negative when travelling west"