diff --git a/fsl/fsleyes/displaycontext/canvasopts.py b/fsl/fsleyes/displaycontext/canvasopts.py
index 2f7e214eac651cf182c4f874e67aa8df203fbe00..ed01214067f1c705459b68b152264d7d79087267 100644
--- a/fsl/fsleyes/displaycontext/canvasopts.py
+++ b/fsl/fsleyes/displaycontext/canvasopts.py
@@ -58,7 +58,8 @@ class SliceCanvasOpts(props.HasProperties):
     """
  
 
-    zax = props.Choice((0, 1, 2))
+    zax = props.Choice((0, 1, 2),
+                       alternates=[['x', 'X'], ['y', 'Y'], ['z', 'Z']])
     """The display coordinate system axis to be used as the screen *depth*
     axis.
     """