diff --git a/q2_boots/plugin_setup.py b/q2_boots/plugin_setup.py
index c44de8a..b3feec5 100644
--- a/q2_boots/plugin_setup.py
+++ b/q2_boots/plugin_setup.py
@@ -193,7 +193,7 @@
         'data': Collection[SampleData[AlphaDiversity]]
     },
     parameters={
-        'average_method': Str
+        'average_method': Str % Choices('mean', 'median'),
     },
     outputs={
         'alpha_diversity': SampleData[AlphaDiversity]